Umm, no, they are pretty much stock Visual Novels.
The Investigation games are closer to pnc adventure games, yea, mainline Attorney games are just standard VN read and (sporadically) choose some option.
What about the puzzles and the exploration (aka investigations in the mainline games)? The trials are also basically an extended puzzle, present in all of the games as well. This is not a "choose some option", because you have to actually solve a puzzle (by analysing a testimony) to proceed
and there are fail states, whereas in a typical VN most options merely put you on a different path of the branching scenario. And, well, AAI is no different from the main series (despite being boring trite), the gameplay is pretty much the same.
That's entirely unlike, say, Ever 17, which doesn't have any gameplay
at all and even the dialogue choices are not very often (you can spend significant amounts of time reading, before you are even presented with next one) or even 999, which merely features elements of the adventure genre.
The only thing that's different in AA compared to games like Monkey Island, * Quest, Grim Fandango etc is the perspective (first person vs. third person), but they are not very much different gameplay-wise. Unless your definition of a VN is "any first person text-heavy game with anime-like stylistics", of course. In that case AA games indeed are VNs, as is stuff like Etrian Odyssey.
Where does 999 sit in these genres? I haven't played it yet, but have heard it is very good.
It's basically a VN (rare dialogue choices that put you on different tracks) interwoven with occasional puzzle sections, which are more or less isolated from the VN parts.
