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Frank Wakefield#1 2006 Standard Catalog of Baseball Cards, edited by Bob Lemke.
#2 The Encyclopedia of Baseball Cards, all 3 volumes, by Lew Lipset. (Dated, but chocked full of great information.)
#3 This site.
#4 An old copy of Bert Sugar's The Sports Collector's Bible, again dated but useful.
and then, if you've gotten those 4, find a copy of Jefferson Burdick's American Card Catalog. You won't use this with much frequency if you're only after baseball cards, but it is the first milepost for the hobby, it helps you understand that the T in T cards isn't for tobacco... gives you a background for N, T, E, R, M, and the rest of the alphabet soup of card designations.
Just saw your login name, my second car was a 1971 Challanger. Had 2 Chargers, '72 and '74. Mopar was about going forward fast...