It was a tough choice selecting a favorite sex scene from the many books I've read, which don't even include romance novels per se, but who doesn't like a racy love excerpt in the middle of a serious read? It only makes the boring parts better, in my view. In the end, I went with Robbie and Cecilia of 'Atonement' by Ian McEwan as my favorite.
The scene: In the library at night before an evening soiree, the doomed couple of this acclaimed (and film-adapted) novel will have their first and sadly last tryst that, by itself minus most of the rest of the book, stands out as one of the most memorable, evocative sex scenes in literature I've ever read. In a way this act had built up to what I felt was a fitting climax (no pun intended) for the two characters who seem in earlier chapters plain and proper on the surface but virtually seething behind closed doors with pent-up emotions towards each other, you just had the notion the two of them would get it on at some point, and wherever it happened, it would be amazing.
What stood out the most, as I read it, was how plainly the author noted the awkwardness of movement, sound, (creaking book shelves) taste (lipstick and salt), racing thoughts (...He forced himself to remember the dullest things he knew—bootblack, an application form, a wet towel on his bedroom floor...), and raw imagery (their limbs slid across each other in this restless, sensuous wrestling...) and how it all seemed to contrast very beautifully to what typical depictions of sex in literature more commonly portray. I also like how candidly written the not-so-flawless parts of this scene were included throughout, like during the moment of penetration, Cecilia shuts her eyes and looks away from Robbie, or when during a heated moment Robbie attempts to give her rear a 'retaliatory slap' but standing against the bookshelves, there isn't enough space to do it.
One other excerpt that stood out for me was in Robbie's identifying the whole of his physical reaction to the sex as the closest thing to religion he'd ever known, and that's something I believe readers can identify with on a personal level if they've had a similar experience in love. We know the feeling, but learn after the fact what we feel in such moments are mostly just a complex web of biologic responses that elicit such reactions during the act of love. Those reactions are different if you're male or female.
There was sort of a unique eroticism to the sporadic oddness to Robbie and Cecilia's coupling. The two weren't outright in a conventional romance having come from two very different worlds, but had known one another long enough to understand the meaning their actions, to finally express what had long been repressed in each of them, summed very well here: 'When he lifted the clinging, silky dress again he thought her look of uncertainty mirrored his own. But there was only one inevitable end, and there was nothing they could do but go toward it.'