I haven't actually read them yet, but my wife has and she is enjoying them. (yen on in general does a pretty good job localizing them, with just a few typos here and there)
I mean, they are what the anime is based off of, and they really didn't change much from what I know.
they might be the next ones I read after I finish the sword art online ones and no game no life 5 though.
sword art online progressive is going to be interesting to see reactions if it gets animated. (quite a bit different than normal sword art online, though normal sword art online is already decently different from the anime)
Having read both 1 and 2 of the Light Novels they're pretty close to the anime. The first novel feels a bit boring at times, and the writing for it... I dunno, something seems a bit bland in the way the story is told. I actually thought the second was an improvement, but neither really captures what the animation and voice acting brought to the story.
Also, the anime contains, as far as I can tell, a slew of original subplots that aren't in the Light Novels. The late night school episode, the buying stuff online and trying to return it plot, and the trip to the zoo/fan service episode. None of that is in the Light Novels (at least through Vol 2.)
So I wouldn't say they're bad per se, I had fun with Vol 1. and quite a bit with Vol 2, but the anime really is the better experience. In fact the way the the anime wraps you could basically jump into Vol 3 and not be too lost at all.