There are not many options for Notes/Domino administration books. I haven't looked for Notes/Domino R7, but the number of books published has decreased dramatically from Notes/Domino R4 to Notes/Domino R5 and Notes/Domino R6, where I think I found one book a year ago.
I suggest taking a class at a training center, setting up a Notes/Domino server to play with at your desk, as well as becoming active in communities and forums such as SearchDomino.com, Notes.net and LotusUserGroup.org.
You should read "Lotus Domino Administration in a Nutshell," written by Greg Neilson and published by O'Reilly Media. I recommend it for Lotus Domino administration, even though it was already released in 2000 with version R5.
Also, BookButler.com is a very good site to search for Lotus Domino administration books.
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This was first published in February 2007