The game is slow, sure. But this is what I had come to expect. I played the first game on the 3DS, then re-watched the movie again, then played this game. The movie is really just a truncated version of both games put together. But, if you're into the world of Ryme City and the personality of Detective Pikachu himself, then you're in for a good time.
It's a very relaxing game, with no thinking needed on your behalf, which can help if you've had a long day and just want to do something to wind down.
Take note of what I said above, as Detective Pikachu's character is really fun and enjoyable. However, the rest of the characters are paper thin in personality, which can make the game a little boring sometimes. I do however enjoy how they put some personality into the Pokémon themselves, and having Detective Pikachu himself conversate with these Pokémon, it's a nice little touch.
If you love Pokémon and/or enjoyed the 3DS game, then this is certainly for you. If neither of these, then I wouldn't recommend getting it.
Solid 4/5 from me.