This collection can be split in 3 ways. Firstly there are general, Cthulhu Mythos related stories, then there are Titus Crow ones (which are not included in the Titus Crow novels), and finally there are 3 set in Brian Lumley's 'Primal Lands', a Sword and Sorcery take on the Cthulhu Mythos.
I liked this book, but fair warning, I did already have some of the stories in other collections. If you're a Brian Lumley fan, odds are at least some of these stories will already be familiar to you. Also, a couple of the stories included here have actually appeared in some of his novels as chapters - from The Burrowers Beneath and Clock of Dreams (I think). As I don't have those novels myself, I didn't mind, but again, something to be aware of.
Still, I can't fault the quality of what you get here. It really is a comprehensive collection, and a great companion to The Taint, his collection of Cthulhu Mythos novellas. I preferred the Titus Crow and Primal Lands stories myself, but really, there are no duds here.
I've read his Necroscope, Psychomek and other novels, but have only got into his short stories fairly recently. Haggopian is a good addition to the them, and would make a good introduction if you haven't read any of his before.
Now I finished it, I will be seeing what other Brian Lumleys are out there to read - and isn't that what collections are supposed to do? Enjoy