Heritage is the 5th EFC book, and almost certainly the best.
While "Arrival", "The First Protector" and "Requiem for Boone" focus on event before the show, and "Augur's Teacher" focuses on an original chracter, "Heritage" is purely about Liam.
The basis is that Zo'or's latest project is to give humanity shaquarava through a virus, shortly after the season two episode "Second Chances". (Shaquarava are the glowing things on Liam's hands, for those unfamiliar with the series) Not knowing that Liam is one-third Kimera, and has shaquarava of his own, Zo'or orders that Liam is administered the virus. The virus gives Liam access to some of his genetic memories, including the knowledge that it was the shaquarva that turned the Atavus into Taelons, and started them on that nasty treacherous path of theirs.
Hayley Simmons (from episodes "Second Chances", "Thicker Than Blood" and "Take No Prisoners") is a major player, and there are bits of Liam/Hayley romance. While it is questionable that Zo'or would attempt to give humans shaquarva (which could allow humanity to join the Commonality), this is a minor flaw.
The plot is mainly plausible, executed with a minimum of techno-babble, and makes sense in context with the rest of the series. There are excellent explanations for the Taelons' hatred of the Kimera and how the Taelons and Jaridians differ. All characters are very, umm... in character.
Anywho. It's a great book.