The BON is regarded by most as the definitive guide for Tigers, especially factory production, configuration and available options. That said…it is pricey to say the least.
Since you are on the TEAE forum,I should recommend you join TEAE. Attend our annual gathering or a regional event. Where are you located? I am sure there are owners in your area who are more than willing to share info and provide assistance. We are also on Facebook.
I agree with Jim. The BON has loads of great info but seeing cars up close and talking to long time owners and taking photos will get you enough knowledge to tell what you are looking at when you see cars for sale. If you are near South Carolina come join us this Friday and Saturday at our SOS/Invasion. Over 20 Sunbeams will be there!
After saying all of this, I have a nearly perfect BON signed by the author for sale. And like Jim said, it is pricey!
Joining TE-AE is a great first step (that’s what we did "back in the day" 😀 ), will give you access to all of the Club members names/locations/car listing, etc. There are some very knowledgeable folks up there!
Also, the club Facebook page is more active than this forum at this time…