While the NASA MESSENGER orbiter mission collects initial data to reveal Mercury's secrets (like the Cookie Monster crater), there will be a long wait until this information is published in the Space Science Series [and it will cost quite a bit: 60 - 80$].This book in the Space Science Series is the "before" book, at a very reasonable price. So if you want to know what we knew about Mercury before MESSENGER's 3 flybys and many orbits; and appreciate how hard your tax dollars are working in producing the marvelous new insights MESSENGER has garnered, then this is the book for you!The same can be said of Pluto. Most Space Science Series books on planets are ~1,000 pages with detailed information [and equations!] about all aspects of that planet: surface; magnetosphere; atmosphere; moons [if there are any]; etc. The before book on Pluto is only 250 pages, and is more about what we don't know about Pluto [but would like to], and why is it so difficult to obtain information about this outlier. The Space Science Series ~1,000 pager on Pluto should be available sometime in 2016. I can't wait [but must, since this information won't be known until New Horizons flies by in July 2015!].