Eh? Why the embarrassment? There are tons of writers out there whose works I've not read; may never get around to (certainly with the backlog I've got now, anyway). As for my comments on Heinlein... I was just thinking about that aspect, having reread "Life-Line" the other day... how he used a very simple approach to elicit some very complex emotions. I don't think it's something he consciously sat down and wrote and rewrote to get that ending (though, of course, he may have done); just that he was well-read enough, and talented enough, to be able to strike those chords beautifully, with such seeming simplicity.
Also... I overanalyze....
Lovecraft... that's a difficult one to answer, as different people find different stories to their taste. For most, though, I'd not suggest beginning with
At the Mountains of Madness;
The Case of Charles Dexter Ward might be a very good novel or, if you're in the mood for more of a fantasy piece,
The Dream-Quest of Unknown Kadath. But probably best to start with some of his earlier short stories before getting into the Mythos stuff (which begins, really, with "The Call of Cthulhu" in 1926 -- though he continued to write other types of tales for some time still. On the other hand, "Cthulhu" was my first real encounter with HPL, and it obviously stuck. I'd also highly recommend "The Colour out of Space"; very nice, that.
Penguin Classics have a nice three-volume set that has most of his work. But, before you decide whether or not to spring for something like that:
The H. P. Lovecraft Library
And:
The H. P. Lovecraft Library
I'd suggest using the first to link to his stories, as there seems to be a glitch in the second with some -- try linking to "The Alchemist", for instance, in HTML format, and it takes you to "Azathoth" (though PDF seems to be fine). But the second also has quite a bit of his poetry and some of his essays, including his treatise Supernatural Horror in Literature", along with a bibliography for that which includes links to quite a few of the tales he discusses.
The first link, as it's chronological, begins with his juvenilia (from age 7 up), so you may want to skip the first few and start with "The Tomb" -- although "The Beast in the Cave" is very good for a 15-year-old, and "The Alchemist" isn't any too shabby for a teenager, either.