There are reference books, but no prior exam questions
If you take LPIC exams, you are also pledging not to go use prior exam questions or to visit web sites that advertise to have these. It is considered a breach to do so.
Your best bet is to get a cheap test system and some certification books. The certification sub forum has a lot of discussion on which exam is the best to take. LPIC certification texts are available from many publishers, including O'Reilly.
I'm also hoping one of the moderators will move this to the Certification forum.