Okay, so I guess I better get to explaining as much as I can remember happening in the first book, known as 'Tigerstar's Reign', but only the important parts.
The entire premise of the book was, what if Tigerstar succeeded in killing Bluestar in 'Forest of Secrets"? And it just continues from there.

Below is the old cover of the book that I created.

Tigerstar's Reign begins right at 'Forest of Secrets', in the scene where Tigerclaw goes after Bluestar in her den, and attempts to kill her.
- Tigerclaw kills Bluestar, and Fireheart is too late to save his leader.
- Tigerclaw drags Fireheart out of the leader's den and announces that Fireheart killed Bluestar.
- Cats are shocked, some disbelieving, but are convinced by Dustpelt, Longtail, and Darkstripe that Fireheart is Bluestar's killer.
- Tigerclaw orders Longtail and Darkstripe to kill Fireheart.
-Fireheart is brutally murdered by Longtail and Darkstripe.
- Cloudpaw is exiled from the Clan for being a kittypet.
- Tigerclaw goes with Yellowfang to the Moon Stone.
- StarClan, unable to disprove of Tigerclaw's new leadership, give him his nine lives.
- Tigerstar becomes the new leader of ThunderClan.
- On the way back from the Moon Stone, Yellowfang challenges Tigerstar. Enraged, Tigerstar kills Yellowfang and leaves her on the WindClan border, covering her in the scent of heather and barley. Tigerstar gives himself claw marks and rubs himself against WindClan scent markers, and then runs back to ThunderClan.
- Tigerstar arrives at ThunderClan in tatters. Cats are shocked when he announces that Yellowfang is dead, killed by WindClan warriors.
- Tigerstar announces a war on WindClan.
- Days after Yellowfang is burried, Tigerstar announces to the Clan that they are going to attack WindClan.
- ThunderClan attacks WindClan.
- Tallstar loses a life to Tigerstar.
- On the side, Greystripe turns on Tigerstar and yowls at him, accusing him of murdering Fireheart.
- Tigerstar knocks Greystripe to the ground and kills him, declaring him a traitor that turned on him to be on WindClan's side.
- ThunderClan wins the battle against WindClan.
- Four moons of peace pass.
- Brightpaw, Thornpaw, and Swiftpaw are named warriors, Brightheart and Swiftfur, and Thornclaw.
- Dustpelt and Sandstorm become mates.
- Sandstorm is expecting Dustpelt's kits.
- ShadowClan is left leaderless and scared, after their previous leader and deputy die of greencough.
- Tigerstar takes advantage of ShadowClan, and join ShadowClan and ThunderClan into one Clan, known now as TigerClan.
- At the Gathering, Tigerstar announces of TigerClan. Leopardstar and Tallstar are suspicious, and have their doubts about this.
- Two more moons pass.
- Sandstorm gives birth to Dustpelt's three kits, Brownkit, Cloverkit, and Eclipsekit.
- Tigerstar begins to take an interest in Eclipsekit.
- Two more moons pass.
-TigerClan remains strong, though some cats have left to join WindClan and RiverClan out of fear.
- Tigerstar goes to the twoleg place and finds Scourge.
- Tigerstar makes a deal with Scourge, promising him territory in the forest if he helps to get RiverClan and WindClan on their side.
- At the next Gathering, Tigerstar declares war on WindClan and RiverClan.
- Leopardstar and Tallstar do not back down.
- One moon later, Tigerstar goes onto the battlefield with BloodClan and TigerClan at his side.
- Leopardstar, intimidated, immeadiantly gives in and announces her alliegnce to TigerClan.
- WindClan refuses to back down.
- TigerClan and BloodClan attack, nearly everyone is wiped out from WindClan.
- Tigerstar kills Tallstar until he has no lives left.
- TigerClan takes over the forest.
- BloodClan is given ShadowClan's old territory.
- TigerClan resides it's main camp in the old RiverClan camp.
- Brownkit, Cloverkit, and Eclipsekit are ready to become apprentices. Brownkit becomes Brownpaw and is Longtail's apprentice. Cloverkit wants to become a medicine cat and is named Cloverpaw, as Cinderpelt's apprentice. Eclipsekit is named Eclipsepaw, and becomes Tigerstar's apprentice.
- Two moons pass.
- Tigerstar gathers up all the half-Clan cats in the camp and places a kill order on them. Darkstripe and Blackfoot kill Stonefur and Mistyfoot. Eclipsepaw, desperate to prove her loyalty, kills Featherpaw and Stormpaw.
- All traitors in the camp are treated as prisoners.
- Once TigerClan is up to par, they engage in battle with BloodClan. Tigerstar kills Scourge, and the BloodClan cats scatter.
- Tigerstar names the home of TigerClan at the Gathering place.
- Five moons of peace pass in TigerClan.
- Cats of TigerClan begin to train in the Dark Forest.
- Brownpaw and Eclipsepaw pass their assessments and are named warriors, Brownscar and Eclipsecall.
- Morningflower, a previous WindClan queen, gives birth to three kits, Flowerkit, Dawnkit, and Flamekit. 
- More moons of peace pass.
- Twolegs begin to encroach on TigerClan territory.
- Eclipsecall receives a vision from StarClan, telling her that twolegs will destroy the forest, and TigerClan must move.
- Eclipsecall and Tigerstar fight over Eclipsecall's dream, Tigerstar believing it's not real.
- Twolegs begin to destroy Clan territory.
- Twolegs destroy TigerClan camp.
- Tigerstar leads his warriors to find a new place to live.
- After a moon, TigerClan finds the lake territories. Many cats were lost on the journey there, including Leopardstar.
- During the journey, Eclipsecall and a warrior named Ashfur become close. They soon become mates.
- TigerClan settles around the lake.
- Flamekit and her siblings are ready to become apprentices. Flamekit is named Flamepaw, and is apprenticed to Eclipsecall.
- Through the six moons of Flamepaw's training, Eclipsecall and Flamepaw realize the horrors of TigerClan as Tigerstar becomes more violent, and begins to kill innocent cats.
- Flamepaw becomes a warrior with her siblings. Flamepaw becomes Flameburst.
- Eclipsecall is expecting Ashfur's kits.
- Eclipsecall gives birth to Ashfur's kits, Jaguarkit, Lilackit, Sharpkit, Birdkit, and Raccoonkit.
- Eclipsecall becomes terrified of Tigerstar, and raises her kits as safely as she can until they become apprentices.
Eclipsecall begins to form a group of cats in secret that are willing to rise against Tigerstar.
- Moons pass of Eclipsecall and her secret group forming plans to take out Tigerstar and TigerClan.
- On the night of a full moon, Eclipsecall and her group of cats now known as LightClan, descend on the TigerClan camp.
- Tigerstar orders the still loyal members of TigerClan to kill all LightClan warriors.
- The battle rages on. Eclipsecall comes face to face with Tigerstar.
- Eclipsecall and Flameburst both attack Tigerstar, and take all his remaining lives from him.
- Tigerstar dies.
- TigerClan gives up. The battle is won by LightClan.
- Eclipsecall takes charge, and begins to divide the lake territories into correct portions for the original four Clans.
- They find the Moon Pool, and the new leaders are chosen.
- Eclipsecall is appointed to become the new leader of ThunderClan.
- Scorchfury is appointed to become the new leader of ShadowClan.
- Wolfblaze is appointed to become the new leader of WindClan.
- Blizzardhowl is appointed to become the new leader of RiverClan.
- The cats of the previous TigerClan and LightClan all decide upon which Clans they choose to reside in freely.
- Once camps are established, Eclipsecall finally settles down in the ThunderClan camp with her mate, Ashfur. It is the night before her nine lives ceremony, and she knows that things will be looking up for all the Clans for some moons.

And yes! That is basically the entire story of 'Tigerstar's Reign' summarized.
And now, it's time to continue a new chapter, in the book 'Warriors ; Super Edition : The Black Panther'.