Cuisine/Geographically, with neighboring cuisines near each other, which is challenging as geography isn't linear but bookshelves are -- more or less. :-)
Nothing alphabetized, though multiple books by the same author are grouped together unless they are in radically different cuisines (e.g. Naomi Duguid's books, which are all over the place). I have about 350 books - a good sized collection, but not yet over-running the house. I did reorganize recently because my Asian section outgrew its space and had to move.
One section goes roughly east to west from Japan to India: Japanese, Korean, Chinese, Macanese, Indonesian, Malaysian, Vietnamese, Thai, Burmese, Nepalese, Indian, Sri Lankan, Pan-Asia books. This covers about 50% of my collection.
Second section covers general western (e.g. Joy of Cooking, Bittman, etc.), then roughly west to east this time: Portugese, Spanish, Northwest Med/Southest France, French, Italian, back to Morocco and general North African, Middle Eastern, Turkish, Persian, up to Russia, and finally Central Asian.
Non-Mediterranean Africa: Senegal, Ghana, Ethiopia, Eritrea, Somalia, South Africa, Pan-African books.
Americas: Native American, regional US (e.g. Southern), Mexican, a few cookbooks for South American cuisines, Caribbean
Baking shelf
Oversized shelf, including my binders of hand-written, printed, and magazine recipe cut-outs
Third section is miscellaneous: preserving/canning books, those church and community cookbooks, a few random general cookbooks that I don't use often, food companion/ingredient encyclopedias, tips & tricks books, odd books like Salvador Dali's cookbook, Alinea, Modernist, and really old cookbooks.
Forth section: food history, culture
Magazines are organized by publication and date in magazine shelving boxes.