Out of all the cool loot I got in the Swords & Wizardry Complete Kickstarter, Monstrosities is probably the coolest. I think I like it better than The Tome of Horrors Complete, and that's saying a lot.
See, Monstrosities is for the most part, your usual "D&D" monsters with a fresh coat of paint and a "hook" for each of them. Me, I love the hooks. I loved them in ToHC and I love them here. They are enough to riff off of, and I am, if nothing else, a DM that enjoys the challenge of improvising.
Now, if you have the older S&W Monster Book, much of what you get here was in there. It's just presented in a more enjoyable fashion, with each monster getting it's own page, art and hook.
Here, let me show you an example from both books:
|From the S&W Monster Book|
|From the S&W Monstrosities Book|
I really like the second presentation :)
It comes in PDF and Print flavors. PDF at RPGNow, Print with free PDF at Frog God.
Personally, I'd go with the Print and PDF, as the book is fairly massive and nice to hold and a decent value at $50 for the 500+ page hardcover book and the PDF. Still, you can't got wrong if you get it either way. You'll get some good use out of it, especially the hooks if you are anything like me.