Even as a semi-frequent consumer of visual novels, there are few that I would recommend almost unreservedly. Steins;Gate would be one of them - a time-travel mystery/thriller that (one character arc aside, which is a bit tone-deaf to contemporary gender issues) contains very little in the way of overbearing anime cliche to wade through. Its sequel, Steins;Gate 0, launched on PC yesterday, continuing the tale of young self-described 'mad scientist' Rintaro Okabe through a potentially doomed timeline.
Rather than pick up after the happiest possible ending of the original Steins;Gate, 0 returns to follow our protagonist through a partially failed branch in the timeline. Not everyone survived this time round, and the predestined World War 3 now seems inevitable. Okabe is also shaken from his less-than-cheerful adventures through time and space in the previous story. Gone is the irrepressible teen wunderkind, his experiences transforming him into a rather sullen and morose university student. Less mad scientist, more sad scientist.
While time-travel and parallel worlds are still a key focus of the story, the third string added to Steins;Gate 0's repertoire of sci-fi standards is advanced, potentially sentient artificial intelligence, and all the many implications of it. As with the first game, there's a decent amount of interactivity and enough minor and major plot branches to lead to six possible endings, although for the most part you'll just be doing a lot of reading. Steins;Gate, while largely self-contained is also part of Mages' Science Adventure series, which now encompasses five (soon to be six) main VNs, plus several non-canon side-stories.
For those of you who aren't feeling up to a lengthy read, the anime adaptation of Steins;Gate 0 recently started airing on Crunchyroll. While I've not had a chance to look at it myself, the original Steins;Gate adaptation (sadly unavailable in the UK) was surprisingly solid, if perhaps a little too heavily abridged in places. A remastered version of the original Steins;Gate is also due out some time this year, featuring art, audio and video from the animated version in place of the original materials, plus several newly translated extra stories.