These are two more in O'Reilly's Pocket Reference series. There is not very much to say about them which is why I am writing this rather than burden someone else with the review task.

If you are new to a subject then a Pocket Reference will not be of much use to you. If you are an expert, then you would know the contents anyway. If you always work with your reference library to hand then you will have more detailed references within reach. However if you are an occasional user of, in these cases, C# or JavaScript and do so when away from access to your reference library then these books are pocket size and their weight is unlikely to damage your pockets.

I wish O'Reilly would parcel books like these with their more substantial 'In a Nutshell' corresponding volumes. That way you would have the fuller reference for normal use but could slip the pocket reference into your pocket when called upon to work somewhere else.

There is nothing wrong with either of these books, but I cannot see any compelling reason for most to buy them.