There are so many ways to alter books so despite what ever route you may decide to go, will be the right way because there is no "right" or "wrong" when it comes to altering something.
You can use a blank pre-made book or journal, or you can use an old book. You can also bind your own book, you could use a little journal from the dollar spot at Michael's, or you could use a spiral bound notepad. Really, your options are only limited by your imagination.
I'm posting a couple of links to help get you started. Don't be intimidated by some of the things you see ~ it's all about playing and experimenting and finding what you like.
Go Make Something
Sky Blue Pink
Karen's Whimsy