It has been a long time since I read anything by Wallace, but as I recall, he was generally quite good. He is primarily known, of course, as a very popular crime writer and the co-creator of King Kong. A rather prolific writer who dabbled in different fields; almost always entertaining, not infrequently several notches above the average of his time.
Amyas Northcote was a contemporary and friend of M. R. James, and his stories have usually been considered "in the James tradition"... which I'm not entirely sure I agree with. He only wrote a small handful of tales, the most famous of which is "Brickett Bottom", about a phantom house. Quieter than most people are used to these days, his stories may seem to lack a "punch", but are thoughtful, well-knit, and (paradoxically) understatedly but powerfully atmospheric... something like some of Le Fanu's ghostly tales in that regard....
I'd have to know what the contents are of the Onions, as he wrote a fair number of ghostly tales, including what is probably the single best example of the form in the English language: "The Beckoning Fair One", one of the most finely crafted novellas out there, and an almost textbook example of the "psychological ghost story". Others also tend toward this end of the spectrum, and vary from brilliant gems to pieces which just manage to misfire....
Crowley... I've only read Moonchild among his fictions (and that was nearly thirty years ago), so I'm not qualified to comment on that one, save to say that, if his shorter works follow his patterns there, you're in for a very strange ride; alternately poetic and powerful or terribly awkward and numbing. At his best, though, quite good.
I must say that, as the series continues, I am glad they also continue to include lesser-known writers of the field as, though there is a reason they are less well known, they often wrote some delightful tales, and occasionally one comes across a true stroke of genius in their writings....
