Actually, Lovecraft does mention MacDonald, though he concentrates on
Lilith: "George Macdonald's
Lilith has a compelling bizarrerie all its own; the first of the two versions being perhaps the most effective" (
The Annotated Supernatural Horror in Literature, p. 57).
Joshi notes, however, that the earlier version has yet to be published, and HPL was going on a paraphrase (which is probably why he qualified his statement). I've yet to read
The Princess and the Goblin (or any of Macdonald's other longer works except for
Lilith and
Phantastes, both of which I would recommend -- though I prefer the former more than the latter, I must admit), but I've yet to encounter negative comments on it save for his usual tendency toward allegory. His short fairy tales are also of interest.
On the subject of Hoffmann, I'd also suggest the E. F. Bleiler collection
Best Tales of Hoffmann as a good introduction to the variety of his work; such tales as "The Mines of Falun" and "A New Year's Eve Adventure" are quite memorable (if at times a bit whimsical as well); and, of course, there have been several new editions of his work over the past few years. especially those from Penguin and Oxford, I believe (though I've come across some things on the recent edition of
The Devil's Elixir -- not by either, I hasten to add -- that give me pause).
I'm not familiar with Preussler at all, but would be interested in any information. As for other weird work that HPL didn't mention... there are tons of Victorians and Edwardians he left out of his essay, and many of these have been recently been brought back into print. One such venture is the Wordsworth Editions of Tales of Mystery and the Supernatural, which has become a rather sizeable series at this point:
[
www.wordsworth-editions.com]
And, of course, such places as Ash-Tree Press, Tartarus Press, and Midnight House/Darkside Press have brought out quite a lot in the field, many of which have been forgotten or overlooked for some time. It is especially nice, for instance, to have a couple of new collections by Edward Lucas White, not to mention a selection of the best of W. C. Morrow and Robert S. Hichens, as well as Joshi's selection from the supernatural tales of Sir Arthur Quiller-Couch....