William S. Monroe, Curator of Medieval Manuscripts and Early Printed Books at the Brown University Library, writes about his discovery that one of the Library’s books belonged to Bernardo Bembo:
Cecil Clough once noted that we can learn much about the life and travels of Bernardo Bembo from the books he owned, especially “because of his tendency … to make biographical jottings in his manuscripts.” In another remark in the same article, he states that “interestingly enough there is no printed book that certainly can be associated with Bernardo’s library.” Now, thanks to Bernardo’s well-known habit, we can say that the second statement is no longer true.
The Annmary Brown Collection at the Brown University Library holds a copy of Augustine’s De civitate dei printed in Venice by Johannes and Wendelin of Speyer in 1470. The colophon to this edition notes that the printers come from Speyer. In the margin next to that colophon, is an inscription noting that two persons were passing by Speyer on the Rhine and decided to sign this book. The inscription reads: “D. Justus et B. Bemb. dum é regione Urbis Spire essemus internavigantes M.ccc.lxxi. xviiii. augusti . librum Signavimus.”
The date was 19 August 1471, the year after this book was printed in Venice. B. Bemb. is an abbreviation often used by Bernardo Bembo, who left Venice on 16 July to be the city’s ambassador to the Court of Burgundy. But who was “D. Justus”, and could the book have belonged to this person rather than Bembo? The second question is more easily answered. There are many more marginal notations in the book, mostly taking the form of indexing. These marginalia were made by at least two hands, and one is identical to that in other books (manuscripts) known to have belonged to Bernardo, as are many of the other marks, such as manicules. Moreover, on fol. 59v are the words of Bembo’s motto: Virtue & Honor.
As for D. Justus, I would suggest two possibilities. The most likely is Giusto de Baliis da Lendinara, to whom Bembo wrote some letters, and who was mentioned in others. Another possibility, but less likely, is Justus of Ghent, a contemporary painter. Justus of Ghent (or Joos van Wassenhoven) painted for the Duke of Montefeltro, having left Ghent for Italy in 1469 or 1470, and known to have been in Urbino between 1472 and 1474 working on his masterpiece, the Communion of the Apostles.
At any rate, the volume merits more study, and is available in the John Hay Library at Brown University. To make an appointment to view the book, email email@example.com.
 Cecil H. Clough, “The Library of Bernardo and of Pietro Bembo,” The Book Collector 33 (1984): 302-331. This remark is on p. 312.
 Clough, p. 313. Clough mentions, in a footnote, that he had earlier believed four printed books to be attributed to Bernardo’s library, but now rejects them. It should be noted, however, that a book published just a year later attributes two other printed books to Bernardo’s library. See Nella Giannetto, Bernardo Bembo, umanista e politico veneziano (Florence: Olschki, 1985), p. 356-357.
 Augustine, De civitate dei (Venice: Johannes and Vindelinus de Spira, 1470), John Hay Library, Annmary Brown 230. ISTC: ia01233000.
 This inscription was pointed out to me by my student assistant, Caroline Hughes, while assisting me in recording interesting features of the collection.
 Giannetto, Bernardo Bembo, p. 27.
 For manicules, including the characteristic manicules of Bembo, see William H. Sherman, Used Books: Marking Readers in Renaissance England (Philadelphia: University of Pennsylvania Press, 2008), esp. pages 35-36.
 Giannetto, Bernardo Bembo, p. 29, 401-402, 408.
 Jacques Lavalleye, Juste de Gand: peintre de Frédéric de Montefeltre (Louvain: Bibliothèque de L’Université, 1936), p 40-50. Would Justus of Ghent have travelled back to the Low Countries in 1471? Little is known for certain of his travels, but he would have been known by humanists such as Bernardo, and they could have travelled together.