Like reviewer Inger Watts, I bought this little volume years ago and find myself referring to it all the time. British history is divided by the reign of monarchs and this book brings perspective to the reigns. It certainly isn't everything you'll need to study the history of monarchy, far from it. But there are many comprehensive accounts in print... this is a facts-packed quick review, and as such is invaluable.
For more thorough accounts consider Antonia Fraser's "The Lives of the Kings & Queens of England" (also available as an excellent audiobook) and The Times' "Kings & Queens of the British Isles". The latter has excellent maps to illustrate historical events.