Let me start by saying that if they fix the editing of Fell Beasts Vol. I then I'll happily give it 4 stars. The monster ideas are great, the art is good, and there is a nice mixture of CR's and types. It could have been so good.
However, 1st monster Air Jelly: "feed off of ... plants" - ok, one slip of grammar and an extra space I can forgive.
Blistering Demon - ooh, sounds great! "Reach 10 ft. (Don't list entry if" What? They left part of the TEMPLATE in the stat block and didn't spot it! Also on this one, inconsistent use of 'Burn' (a SA) and 2d6 fire, missing space in 'a25%' and no hint as to whether 'Burn' stacks with itself. This is just sloppy.
Canopic Jar - a line break in the middle of 'hold person' that makes the stat block hard to read.
Ghissic - missing blank line between 'Hive Mind' and 'Host'
Mercy Flower - 'Cha 15' split over 2 lines.
Riverwrath - A missed opportunity to provide a way for a good-aligned party to redeem this poor fey.
For me, Adamant has now established a reputation of throwing unfinished products (this and Tome of Secrets) out of the door to be 'first' at the expense of proof-reading and editing. It makes me wonder if these monsters have been play-tested. I'm also regretting pre-ordering 'Warpath' - I was lucky that the first printing of Tome sold out at Gencon and the pre-orderers got the fixed hardcopy.
I really want to like these monsters, and I'm being so scathing here mostly in the hope that Adamant will read this and improve their QA - there are people here on the boards that would review and edit for them for FREE after all!
Come on guys, fix this PDF so I can post the glowing review the monsters deserve.
As an aside - it may not be in Paizo's style guide, but a subheading between the end of the abilities and the start of the monster 'fluff' would make monster descriptions a lot easier to read.