Sandra Boynton wrote, illustrated and "overresearched" a book published in 1982 called Chocolate: The Consuming Passion. The book isn't really available through Amazon, rather other used booksellers. The ratings on the book are all 5 star and obviously written by other chocoholics.
I've always enjoyed Boynton's characters and she makes full use of them to get across the basics of chocolate. On the back of the book a pig declares "This comprehensive guide answers every possible question about chocolate." While a turkey (the "bad" character in the book) asks "Is chocolate available in nicer colors than brown?" The response by the pig is "This thorough guide answers every intelligent question about chocolate."
And it does! It has the descriptions of the types of chocolates, the horrors of white chocolate and carob, how to evaluate chocolate, the truth behind vanilla ice cream, chocolate profiles, and recipes all with Boynton's cute characters which I've always been partial to. I have several of her board books and buy her Mom's Family Calendar every year.
Boynton makes mention of the Ghirardelli 5 pound chocolate bar (It took me a full month to eat the one I purchased for my 18th birthday.) claiming its title of "World's Largest" isn't accurate. The internet says Guittard's made a 10 pounder and Nestle made one that was 2.67 thousand pounds. I think I'd have a difficult time eating that one! I was disappointed that Guinness doesn't say what the biggest chocolate bar really is. I will need to write a letter.
Anyway, chocoholic + used book store = glimpse of The Consuming Passion.