Reddit reviews The Lurker at the Threshold

I very much liked The Lurker At The Threshold (listed as by Lovecraft, though it's Derleth's), though the ending third of the book gets rather stupid. :/ Robert M. Price "rewrote" that part of the story as "The Round Tower" (available in his book Blasphemies & Revelations ) and did a better job.

The short stories are collected in The Watcher Out of Time and Others; the novel is The Lurker at the Threshold.

I know this will be controversial among Lovecraft fans, but I would encourage you to start with The Lurker at the Threshold.

Why is it controversial? Well, for starters, it is not clear Lovecraft wrote any of it beyond a rough sketch of how it should proceed. Derleth probably wrote much of it. Which brings me to the second reason why it's a controversial choice: It is, in some parts, horribly written, and this only gets worse as you get closer to the end, when it feels downright rushed.

So why do I recommend starting here? Because to me, it has pretty much all the quintessential Lovecraftian tropes: an isolated house in the New England countryside, old Native American legends, the opening of a portal that brings in more than any human can handle, the horrors that Nature herself can present (I never thought whippoorwills or bullfrogs were creepy... until I read this book), and the slow buildup of the horror which, by the end, surrounds you. Oh, and the story is told from three different points of view, which I think was pretty novel for its time. Reading this book is perfect preparation for reading the rest of his works. I think Derleth, being a huge fan of Lovecraft, wanted to give you the full Lovecraft experience (i.e., one that spanned every aspect of Lovecraftian horror), whereas had Lovecraft written this, you would only get one angle, one slice of the horror.

tl;dr: The Lurker at the Threshold is a controversial choice because it is only partly Lovecraft's work, but it fully immerses you in his world.