I was talking about Everworld here. Jake/David are almost identical <>Cassie effectively killed her best friend, the closest thing she had to a sister. She allowed the Yeerks to acquire morphing powers, which they used to kill Rachel (even if they had been elite Hork-Bajir, she dealt a mortal injury to the one who killed her, but he was able to demorph to survive and then deal the fatal blow), and her betrayal of Jake to allow Tom to get away, caused Jake to keep his final plan close to the vest, because he was afraid Cassie, among others, thought he was too weak to do the sufficiently ruthless thing. Rachel effectively admits as much in her last PoV, too.

I didn't think David was that much like Jake, so much as he was an amalgamation of all the Animorphs. Rachel's ferocity, Marco's brains, Cassie's people skills, etc.

Actually, looking back, I realize it is possible there is a David in one of the other books, to whom you refer instead of the renegade Animorph.

I think she also ghostwrote some of those Sweet Valley High books, or Babysitters Club, or something. In an interview somewhere she claimed that she wrote the book where one of the main characters gets her first period or something.

I think it was more of a case as the least invested in the war, and least willing to get her hands dirty. Tobias was the first to want to fight because he saw the Yeerks as evil, Jake & Rachel embraced the fight, and Marco's self-image was really tied up in it, seeing himself as the rational one, and the ruthless one, who'd do whatever it took. Cassie didn't have any stake in the fight, aside from looking out for her friends, and she lost them all. I think her fate was more of a case of representing those who are fortunate enough to survive and move on from a war. There was a lot of lip service paid throughout the series to her being the "best of them all", but her actions seriously undermined that notion, in spite of the willingness of her boyfriend and best friend to give her more credit than she deserved.