As a veteran cruiser, I can honestly say that the Passporter is accurate. I have met David and Jennifer personally and can assure you that they have thoroughly researched everything for their book. IF the book has any additions, changes or deletions, you can access their website for updates.
I only wish that I had mine before my first cruise, but even now I find a lot of information in a very easy and accessible manner with their handy guide.
Regarding booking - book as early as you can to get the discounts, and if you book on ship you can also receive onboard credit. I like sailing in May and October best. Have been Eastern several times - Western was diverted last year but we have two chances this year to get there!
We prefer the 7 night cruises to the 3 and 4 night ones (we have had all three at least once).
We had a Navigator's Verandah for our first cruise (3 night), but have opted to get the full verandah for the others - for many reasons we prefer it.
Depending on how long you will cruise for your first time, you might just see if you like being in an inside stateroom. Because once you get a higher category, I understand it's difficult to take a lower one.
We were privileged to spend time with friends in the Walt Disney Suite and WWOOWOWW! Incredible!
Rae