If you've been logging in using a gaming library that includes dozens / hundreds of PC titles, and can't figure out what to play next, Steam will try and help with a new feature called Play Next.
Unlike Steam Keep recommendations, which tell you what to buy next, now it's gone with your existing purchases and trying to say, well, you already have this, maybe this is what you will be next. There will be three options shown in time, and if you don't book some of them, you can try again (how many tips you'll eventually get depending on the size of your books).
As for how good it is … well, using the new algorithm it's been working on it, the company says "Continuing work … sdon't be surprised if it sometimes shows you unexpected comparison points. ”
Which is great how it worked for me. My first recommendation was Heroes 2 company, given that I've been playing a lot Order of War, Panzer Corps and Hero Company lately it's a good solid thing. Five choices (plus two Batman games) while also complimenting it DOTA Underlords, which is a big no for me, so maybe it's an algorithm that gets its feet.
If you want to give it a try, you can sign in to Steam in the browser and capture your recommendations here.