Highly recommend. I spent 2 hours flipping through reading the book and I have to say I'm astounded that such a high quality product was produced by one person - especially when Tome of Beasts and Volo's have teams of people behind them.
The art is pretty good (there's not always a consistent theme since the sources are a combination of different stuff), but I appreciate having it there.
I can say the lore bits are great and gave me various adventure ideas.
The monsters are well-designed and nothing seems freakishly unbalanced - I would feel comfortable mixing these in my game with monster manual and volo's stuff without fear of inconsistency.
Overall, good product. The $15 dollar price tag was intimidating (never paid so much for a dmsguild product) - but now I understand this is heads and shoulders over what you typically expect from this site and is on part with other professionally released monster books.
[5 of 5 Stars!]