I'm not familiar with the other Zen & the Art of... books.
But, no, Persig's 'Zen/Motorcycle' isn't a self-help book. You won't learn either how to achieve some kind of weird Buddha state or how to fix your motorcycle by reading it. Basically, it is philosophy wrapped inside a narrative where the main character (Phaedrus) travels the country on a motorcycle with his young son & a couple friends ride along as well. There is some human interaction here though that doesn't play as integral a part as it does in 'Lila'. The narrative in Zen/Motorcycle largely acts as a catalyst for extended philosophical rants & theories, as well as flashbacks to the narrator's teaching experience and mental breakdown. Persig himself was certainly a genius and many aspects of both books are autobiographical. At times both books can get a bit long and tedious but never as bad as reading stuff like Kierkegaard or Kant or the like.
If the idea of a modern genius giving a thick dissertation on his understandable philosophy via a fairly compelling storyline intrigues you at all I definitly recommend it. If you like it, I would say trying 'Lila' after that is a must.