Aww, that's okay. I highly recommend it though (when you get the time/money). Probably start with ".Hack//Legend of the Twilight" (Books 1-3) or ".Hack//Infection" (Infection is actually a novel that is part of a 4 book series. It goes Infection, Mutation, Outbreak, and then Quarantine.). That would be the best way to understand the core stories.
After that, there are other main and side series like: - ".Hack//Sign" - ".Hack//G.U." - ".Hack//xxxx" (NOT a hentai. I promise.) XD - ".Hack//Link" - ".Hack//AI Buster" - ".Hack//Roots" - ".Hack//Alcor" - Probably more that I can't remember right now.
Haha! There's quite a bit of reading material there for ya. Most of it is essentially different ways of telling a similar story with different characters, scenarios, backgrounds, and relations. The people are always diverse and interesting to read about as well. It can get a little confusing at times, but for the most part, all the stories blend together in the same timeline. You should start to see similarities and things that tie together in the story-lines after a short time though. Hope you do get the chance to check it out!