Recommendations on -Guides to HP- books?

[slomudskipper <slomudskipper@hotmail.com>]

There are at least three of these type of books that I noticed seemed 
to be selling pretty well (below); I was hoping for the opinion of 
someone who is already pretty well obsessed with the JKR's wizard 
world...

"Wizarding World Press' Ultimate Unofficial Guide to the Mysteries of 
Harry Potter" Mithrandrir & Walters (does this have more speculations 
than what is discussed on HP for grownups? did any of the spoilers 
about book 5 and beyond make you wish you hadn't read?)

"The Sorcerer's Companion" Kronzeks
"The Hidden Key to Harry Potter" Granger
"The Magical Worlds of Harry Potter" Colbert

These are all books that I saw on a bestseller list or were 
recommended by amazon buyers.  Any second opinions?
I got an unauthorized biography for J.K.Rowling one year for 
christmas and it really was disappointing (Shapiro's wizard behind 
the magic).  

Mudskipper