Lager brewing is not that much different from brewing ales. Your yeast and fermentation temperatures are the main differences. Here is a list of books that I have found useful for learning more about home brewing beer. In most of them also contain information of brewing other styles of beer. I think that of all the books out there on brewing you should at least own either Palmer’s How to Brew, or Papazain’s The New Complete Joy of Home Brewing
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New Brewing Lager Beer: The Most Comprehensive Book for Home and Microbrewers
How to Brew: Everything You Need To Know To Brew Beer Right The First Time
The New Complete Joy of Home Brewing
Radical Brewing: Recipes, Tales and World-Altering Meditations in a Glass
Designing Great Beers: The Ultimate Guide to Brewing Classic Beer Styles
Brewing Classic Styles: 80 Winning Recipes Anyone Can Brew
Brew Like a Monk: Trappist, Abbey, and Strong Belgian Ales and How to Brew Them
Wild Brews: Culture and Craftsmanship in the Belgian Tradition