As has been the case for some time, I'm afraid I won't be able to join in with the reading/reviewing of any of these (more's the pity, as I have a great fondness for Conklin's anthologies), but I may still be able to contribute a few things now and again.
1.) I don't think Conklin's can be classed as the earliest sf anthology in hardback;
Adventures in Time and Space came out the same year, but whether before or after I cannot say:
http://en.wikipedia.org/wiki/Adventures_in_Time_and_Space
But both these were preceded by Phil Stong's
The Other Worlds: 25 Modern Stories of Mystery and Imagination (1941), which at least was a blending of science fiction and fantasy:
http://vaultofevil.proboards.com/index.cgi?board=shudderpulp&action=display&thread=52
2.) Long is a writer I feel very ambivalent about. When he is good, he is very good: he can create an atmosphere which is extremely powerful; he often has exceptionally good concepts; and he wrote some of the best "thought-variants" (as such) in the genre. But his execution is very uneven, and even his best often slide into farcically mechanical or wooden episodes now and again, whereas several of his denouements are simply silly.
3.)
Howard Phillips Lovecraft: Dreamer on the Nightside... is an excellent example of Long's strengths and weaknesses at that period... and is, sadly, a very badly botched book (again, despite some very fine things about it). It was, in fact, so badly botched that it had to be heavily revised before publication. Here is what S. T. Joshi has to say about it in
I Am Providence: The Life and Times of H. P. Lovecraft (p. 1038):
[...] although it emerged at the same time as de Camp's biography, was in fact written as a direct response to it. Long read much of de Camp's work in manuscript and confessed to me that he so objected to the portrayal of Lovecraft that he found there that he felt the need to write his own version. Long's is, of course, nothing more than an extended memoir, not a formal biography, and it is flawed on several counts. Minor failings such as silly forays into literary criticism, an unconvincing attempt to recall Lovecraft's exact words on a given occasion, and an embarrassing question-and-answer session in which Lovecraft is made to expound his views on various views can be set aside. What cannot be ignored is the imprecision of Long's memory and the haste with which he wrote his book; the result was that the manuscript had to be exhaustively revised by Arkham House's editor, James Turner, to such a degree that as it stands it is virtually a collaborative work.[/quote]
A rather disappointing practice on the part of a long-time professional writer (though hardly unprecedented).