If you want a book that is all about lemon trees, then unfortunately you are out of luck. However, there are a few books that contain good information about lemon trees. These books typically combine that information with information about other citrus trees or things you can do with lemons.
Lemons: Growing, Cooking, Crafting
"Lemons: Growing, Cooking, Crafting", by Kate Chynoweth and Elizabeth Woodson, has a little bit of everything when it comes to lemons, but does an adequate job covering all of it. It covers both outdoor and container growing and has a specific information on how to troubleshoot problems that gardeners who grow lemons face. Unfortunately, although it was only published in 2003, it is no longer in print and is only available used.
Lemons: Growing, Cooking, Crafting by Kate Chynoweth and Elizabeth Woodson
Growing Citrus: The Essential Gardener's Guide
"Growing Citrus: The Essential Gardener's Guide", by Martin Page, includes a good deal of specific information on lemon trees including the history of lemons as well as information on some of the more popular varieties. Although most of the book focuses on generic information about all citrus trees, Page does an excellent job of putting in specific information that applies to each type when necessary. It covers all aspects of growing citrus including soil, nutrition, pests, disease and growing instructions. It even gives information about how to grow lemons in cooler, temperate climates. The book was published in December 2008.
Growing Citrus: The Essential Gardener's Guide by Martin Page
"Citrus", by Lance Walhein is a good choice for anyone who wants information about the varieties of different citrus, including lemons, especially if they live in the "citrus famous" areas such the Gulf Coast, California or Florida. It does not contain information aimed at citrus growers outside of those areas. The book is light on details on growing citrus and photos that would be useful to help diagnose problems or pests. "Citrus" was published in March 1996.
"Citrus" by Lance Walhein
The Cultivated Oranges and Lemons, Etc. of India and Ceylon
"The Cultivated Oranges and Lemons, Etc. of India and Ceylon", by Emanuel Bonavia is the re-release of a book written and published by Emanuel Bonavia in1888. It includes information on the varieties of citrus fruit grown in India and Ceylon (which is now known as Sri Lanka). Although it is for sale at most major booksellers, it is also available for free through Google Books (see Additional Resources for links).
The Cultivated Oranges and Lemons, Etc. of India and Ceylon by Emanuel Bonavia