Kellogg: “A good deal has been said about Stratford Will’s last will and the lack of anything literary that he left for posterity, but what did the Earl of Oxford leave that links him to the Shakespeare canon, other than his Geneva Bible?”
Hughes: One other book known to have been his has been rescued from oblivion, Francesco Guicciardini’s Historia d’Italia (History of Italy) in Italian. The Folger has it. They don’t dispute that it’s his.
But more important to any consideration of a connection between Oxford and Shakespeare are the books he bought at the same time he bought the Bible, when he was 19 and 20. Records kept by Burghley (Ward 33) reveal that he also purchased a Chaucer, Plutarch in French, two books in Italian, then a few months later, Cicero and Plato in folio (big books), plus paper and pens. Sounds like he was planning on doing some writing.
In 1570, the Plutarch in French would have been the 1559 translation from Greek by French scholar Jacques Amyot, tutor to French King Henry III, from a manuscript in the Vatican. It was Amyot’s version that Thomas North would translate into English in 1579. Oxford knew the Greek and Latin versions of Plutarch from his years with Smith, but if Smith ever had the French version it was missing from his 1566 library list. Plutarch, of course, is the primary source for Shakespeare’s Roman plays.
In Oxford’s time, a manuscript known as the Ellesmere Chaucer was in the hands of Lord North. The most beautiful of all the Chaucer manuscripts, early on it seems it was given as a gift by some member of the 12th Earl of Oxford’s retinue as a gift to Richard III early in his reign in hopes of getting the 13th Earl back to England. Chaucer was Shakespeare’s source for Troilus and Cressida and Two Noble Kinsmen.
As for the books in Italian, they could have been almost anything, the Guicciardini history, Dante, Ariosto, Tasso. One could have been Castiglione’s Il Cortegiano, for the Latin translation of which Oxford would soon be writing a preface. One could have been Giraldi Cinthio’s collection of stories, “Gli Hecatommithi” (1565), that gave Shakespeare a number of plots, one of which provides the basic narrative source for Othello, another the subplot of Measure for Measure.
politicworm 
Oxford’s 1565 of Herodotus (with boar emblem on the cover) was sold at Sotheby’s in 2015. An inscription inside states that Oxford gifted it to Sir Thomas Berkeley.
Is there any research into the “paper purchasing” trail of Oxford, Shaxsper ? (or any writer). Wherever Oxford was printing at any moment would likely have been a “private” source. Curious anyway about where one would buy paper.
Writers bought paper from the Stationer’s Company. When Oxford purchased his French and Italian books in 1569 from William Seres, he also purchased paper and “pen nibs.” Seres was a Master Stationer. Paper was very expensive because it had to be imported from Europe until England got its own paper mill in 1583. There’s a great deal of information here about how and when and with whom he printed his works which you’ll find if you use the search field on the home page. (There was no such writer as “Shaxper.”)