Q. Can you make a siyum when you finish learning any sefer?

A. There are a number of sources for celebrating a Siyum at the end of learning a complete Mesechta (Talmud Shabbos 118b, Bava Basra 121a, Midrash Shir Hashirim 1, Midrash Koheles Rabo 1). Rema (Y.D. 246: 26) rules that when the learning of a mesechta is completed, it is a mitzva to rejoice and celebrate by making a seuda, that is considered a Seudas Mitzva.
On question 271 on making a siyum on Nach, we wrote; Pnay Yehoshua (Brochos 17a) commenting on Rabbi Yochanan’s custom after ending Sefer Iyov, mentions that you should celebrate a siyum at the conclusion of the learning of a complete sefer of Neviim or Kesuvim. So too is the opinion of Minchas Pitim (Y.D. 246,26) and Piskey Teshuvo (1, 194 in the notes) quoting the Avnei Nezer’’s tradition. Haelef Lecha Shlomo (386) rules that you can perform a siyum even on a short Novi with few chapters, and it would be considered a seudas mitzvah as long as it was concluded by happenstance and not planned (as to eat meat in the nine days). A similar opinion is to be found in Igrois Moishe (O.H.1, 57 and O.H. 2,12) where he adds that the learning should be truthful and with some depth.
Horav Shlomo Miller’s Shlit”a opinion is that on the “Trei Asar”, the Twelve Prophets, you have to learn all of them to perform a siyum (question 276).
Some Poskim also maintain that you can make a siyum on ending even a small tractate of mishnayos, when it was learned as a sequence of shiurim. (Daas Torah 551: 10 – Orchois Chaim 470: 3). Others disagree if the seuda is considered a seudas mitzva (Chidushei Rav E. Hidshaimer: Y.D. 246: p. 374).
Betzel Hachochma (4: 99) maintains that it is a seudas mitzva, only if you finished a complete seder, while other assert that you require the complete Shisha Sidrei Mishna. (Minhagim Veremeeza 2: 117).
Leshichno Tidreshu (1: p. 41) relates that the Kehilas Yaakov zt”l would finish every week a seder of mishnayos and would celebrate a siyum on the morning Shabbos seuda. It is of interest that Mishne Halochos (1, 451) opines that finishing any of the great and accepted seforim of Musar, such as the Mesilas Yeshorim or the complete Tehilim when learned in depth (6: 166), is reason for a siyum, as we recite on the siyum declaration: “To start masechtos and other sefarim, and finish them,” other Poskim disagree (Rivevos Ephraim O.H. 189). Taamei Haminhagim (Hilula Derashbi, n. 30) mentions that a seuda was celebrated when finishing the learning of the Zohar.
Horav Shlomo Miller’s Shlit’a opinion is that indeed you can make a siyum and it would be a seudas mitzva, after finishing learning a proper sefer, when and if the learning was not short and casual but extended, dedicated, with some depth and with effort, to the point that it is recognized and considered an achievement.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a