Yeah, I just read the photographic essay book "Spenser's Boston," and the centerpiece of it is a short story in which Spenser and Susan escort Rachel Wallace around town, showing her the sights.
I read (or rather, listened to the audiobooks of) the first five or six of Atkins' Spenser novels, and I agree with you about them. I do recall that one of them (maybe "Slow Burn") had a passage that turned to horror, which to me seemed very out of place in a Spenser novel.
Last year, after I finished reading/rereading the Nero Wolfe novels, I decided to do the same with Spenser. I started buying first editions from The Mysterious Bookshop, but had to stop because they were costing me WAY too much money. The later, more popular novels are fairly cheap - they'll run you $20 or $25, even for autographed copies - but some of the rare early novels from the seventies and early eighties cost hundreds of dollars. The copy of "Rachel Wallace" I'm reading now cost me $2.50 back in the eighties, and it'll do fine.