There may have been less lore in prior paperback/b+w codexes, but I'll say the lore was better.

Heck the rules and units were better in many cases. Codexes have inflated their page count but not the quality is not there, certainly not for the price.
I am also unsure whether I'll buy another codex. I have a healty sized Tyranid army, and despite the new book being near-universally praised, I think I'm just going to do without the book, and get my rules from different sources.