Given the season, the following excellent books on tractate Avodah Zarah are timely. I found R. Ya’akov Wreschner’s Seder Ya’akov immensely helpful. He has since published a condensed version entitled Derekh Ya’akov. Both are available on HebrewBooks.org. I also include the Meiri for his historically significant comments and the collection of Rishonim called Kovetz Shitos Kamai which includes many obscure commentaries:
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Kovetz Shitos Kamai may be indispensable for some- given the problems with the authenticity of Tosfos on Avoda Zara- it contains the unabridged earlier editions of Tosfos. Seder Yaakov discusses that and the issues of censorship that plague AZ and other tractates. I would also put in a plug for R’ Yitzchak Zilberstein’s חשוקי חמד- his שו”ת organized by the daf. It may not so important for fundamental understanding of the sugyot, since it deals with הלכה למעשה -but it’s entertaining. (It’s also on hebrewbooks,org)