There are 4 books in the series but they are not related. The author has some other books as well.
seems live Mocha shut down and changed. Not sure if how it changed is any good.
https://bilingua.io/livemocha-language-exchange
this website says it's the same community but I never used it, so I don't know anything about it.
There's no one 'best way' to learn Italian. If you've never learned a language before, you'll need to try a few difference resources and methods to see what works best for you personally.
A good place to start is with Duolingo. It's not perfect, by any means, but you can learn the basics from there. You might also want to supplement Duolingo with a grammar book. If you're in the UK, I recommend Collins Easy Learning Italian Grammar and Practice. It's an inexpensive book that has really easy-to-understand explanations and lots of exercises so you can practice, with an answer key in the back.
Once you've got the basics, you should find someone to practice with, because apps and books can't talk to you, and if you want to speak Italian, you're going to have to take the plunge and speak. You could find a language exchange with an Italian speaker who wants to practice English, or pay for a tutor who may be better equipped to answer questions you might have.
Buon studio!