Elva, Raglin & Shu-Zen are totally worth booking just on their own merits.

As for the rest, it really depends on where else you might use them.  All of them offer value for Hard FW progression when you get there.  

I wouldn't book dupes just for Forest, but a second Thor would certainly help you in Hydra. 

Morrigaine is all about her passive, she doesn't need books.

Mortu has a block heal on his a1, but even booked it's not 100%. For him I;d say it depends on what other block heal champs you have. But the simple fact you have morrigaine (i regret skipping her fusion) means it's probably not worth booking mortu to be a heal blocker. Kytis, Rowan, and Veno are all epics who are better choices for it than mortu anyway.

Whatever you decide, and I agree with wiley and rat, book them during training tournament NOT events (no points)

I am sure Trips meant to say "Book Over PR CVC"  😂

That's my new definition of early game, still saving/using resources for cvc.

yeah, I've reached the point where if i need to grind cvc points i just gem energy potions and run hard spider 10 or shogun 25

Booking and pulling fragment champs get saved for fusion tournaments

Early Game Forever.  

To each his/her own.  

Points for Books in a Champ Training Tourney are pitiful. 

I am gonna do 400K+ every PR CVC no matter what, so I'd rather take my 3k/Lego Book there than the paltry 200 you get for a Training Tourney.

I plan to build a 2nd Thor with 6 pc merciless for hydra.  

Yeah, I'd probably build a dupe Thor just for hydra if i pulled one.