50 Tips & Tricks for MongoDB Developers is a new offering from O’Reilly in the shorter (66 pages in the ebook format) but more current format they seem to have recently adopted.
The audience for the book is described as those who know the basics of MongoDB, but need to go further. In my opinion, it would be most useful to developers or users who have implemented at least one application beyond the samples and quickstart materials at mongodb.org. If you have not actually used MongoDB for even simple test applications, many of the tips will be academic exercises, nice to know, but not necessarily immediately applicable.
As for the tips themselves, your mileage may vary according to your application needs, but there is a nice mix of topics, from design to optimization. The author’s writing style is direct and most examples are straightforward and easily assimilated.
Since I have used MongoDB only for testing and small in-house applications, my only gauge of accuracy was in the tips related to indexing. The text matched my experiences with the product. Kristina Chodorow, the author, could be considered somewhat authoritative as she is the maintainer of several Mongo drivers (typos excepted).
Overall, yes, you can find all this information on the internet, but the book will save you time and appears to be offered in e-book format at a reasonable price point.