This is an excellent resource that belongs in every keyboard player's library.
The book starts with a nice tutorial on basic chord theory.
The "encyclopedia" part of the book is great, because they include a chord diagram, both treble and bass notation for the chord, and a picture of the treble fingering. They even spell out the notation, so if your sight reading skills aren't the best, you can still read the chord.
One thing to note is that the book is only about 5&1/2" x 8", so the diagrams and pictures are on the smallish side. This was probably done to save costs. For a reference work, I would have gladly paid a higher cost for a larger format.
Another thing to note is that there are some errors in here - for example, the chord chart for E first inversion (pg 132)shows G# as the first note, and in the accompanying photo, the thumb is playing a G. Hopefully there are few such errors.
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Note to Kindle Users:
This book is also available in Kindle format.
The diagrams look "ok" on the Kindle Fire (again smallish), but when you zoom them, they are very low res. Too bad...