The work is inspired by the personal collection of the author, which was supposed to be the foundation of the private Museum of Fine Books, and whose realization was interrupted due to administrative obstacles. The very idea of the book as a museum and art object has been emphasized in several works by the author, so this is more a combination of beautiful and rare books as sources of new knowledge presented in a personal way, as the collection was created. Due to the size of the text and the amount of illustrations in this issue of the Osječki zbornik, we are publishing the third of the paper. The term “beautiful book” is often associated with Henry D. Kahnweiler, who in 1909 began publishing a series of books by famous avant-garde contemporary writers (Guillaume Apollinaire, Max Jacob, André Malraux, Erik Satie, Gertrude Stein, Tristan Tzara, Maurice de Vlaminck and others) illustrated by avant-garde contemporary painters (André Derain, Pablo Picasso, Fernand Léger, G. Braque, E. Lascaux, Juan Gris, Maurice de Vlaminck). On the occasion of the 50th anniversary of D.-H. Kahnweiler, a brilliant small catalog was published in 1959 at the Galerie Louise Leiris (November 13 - December 19, 1959). Its content, as well as Kahnweiler’s dedication to Ivo Steiner and his wife Odette Masson (maiden Cabalè), “made” me start a “crazy project” of collecting beautiful books. Well, some others as well! The selection of books related in any way to Croatia, i.e. Croatian writers and painters who illustrated them, was perhaps the most difficult, and in the end, some of them may not be considered very beautiful books, but as the criteria are very diverse, perhaps there are more beautiful examples which are left for some ther occasion, and to me the more interesting ones are presented here. Thus, the book dedicated to Silvio Strahimir Kranjčević “Poems” is exceptionally illustrated and with many additional interesting details, perhaps the best example of a “beautiful book”, while “Bridges of the Elite” by Mirko Kus-Nikolajev is primarily interesting illustration on the cover of Slavko Kopača from 1940. In a way, this also applies to Ljubo Babić’s cover for August Cesarec’s “Emperor’s Kingdom” from 1925 and Milivoj Uzelac’s cover for Herbert George Wells’ “Battle of the Worlds” from 1923, which, despite their artistic qualities and modernity, are true small artistic masterpieces. The book “Donkey in Love” by Louis Couperus” from 1923, with three cooper etchings by Marijan Trepše, despite being a modest technical work, is nevertheless a true example of a contemporary, artistically illustrated beautiful book. Marijan Mikac’s book of Zenitist poems, published in Belgrade in Cyrillic in 1923 (“Zenit“ Edition), “Effect on the defact“ (Efekt na defektu”) may be the least beautiful book, but it is certainly the most special for several reasons. This rare edition of the Croatian writer and cultural worker Marijan Mikac, in addition to its artistic and political current affairs (Dadaism/Zenitism; Zagreb/Belgrade), has a great cover illustration by Jo Klek, i.e. the Croatian architect and contemporary artist Josip Seissl, who most likely did the entire Dadaist /zenitistic typography. I chose “magic formula 6 + 6 + 6” as a selection from our small collection of beautiful books and publications to try to conjure up the term “beautiful book”, but also because the selected books have some links with our artists, writers, people and events, and who have left their mark on them in various ways. The printed content of books here is mostly just illustration to illustrations, and notes, dedications, covers, illustrations, information about the book as an object (number of pieces, type of paper, publisher, printer, price, etc.) are actually a topic or riddle to be solved.