In 1935 the nursery was converted into a library. Even Aino Sibelius was surprised to discover the number of books her husband had acquired.

Over the decades, Sibelius’s favourite writers were Goethe and the ancient classical authors such as Homer and Horace. He had studied Greek and Latin and become acquainted with the writers of classical antiquity during his school years in Hämeenlinna. According to Aino Sibelius, the composer’s favourite reading was Homer’s Odyssey in Latin.

The majority of the books are in Swedish and Finnish. Sibelius also read German fluently, French quite well and even English at least passably well. In the library there is literature in all these languages.

The works of the contemporary Finnish writers Juhani Aho and Eino Leino, as well as those of many other friends of Sibelius, often contain a dedication. The dedication by F. E. Sillanpää continues from one of his works to another.
Aleksis Kivi, Minna Canth and Arvid Järnefelt are well represented. So too are Sibelius’s favourite poet, J. L. Runeberg, and many other Swedish-speaking poets of Finnish nationality. As for Swedish authors, between the pages of August Strindberg’s Svanehvit there is a manuscript, which the author sent to Sibelius: it contains the revised ending of the story.

The composer was presented with many books on music. He appears to have had a fairly complete collection of books about his own works.

In 1916, the composer considered Erik Furuhjelm’s recently-published Sibelius book to be a suitable Christmas present. On the shelf there is copy for Linda Sibelius containing his own dedication. There are several copies of Karl Ekman’s books on Sibelius, and the composer made minor additions and corrections to them. The biography of Robert Kajanus by Yrjö Suomalainen is in the downstairs study. The composer wrote a vigorous protest on the page in which Kajanus claims to have advised Sibelius on composition.

There is a complete set of Shakespeare’s works in the library. In the pages of The Tempest there are several notes, apparently in his daughter Ruth’s handwriting. Ruth played Ariel when The Finnish National Theatre staged The Tempest in 1927. Another author who is well represented is Schiller.

Sibelius liked to show his guests a Japanese deluxe edition of Kalevala, which contained a dedication by the Japanese translator Kokita Morimoto. He was also especially proud of the dedication that Mannerheim wrote in his book Journey across Asia. The dedication goes as follows: “To the Master of Melodies, Professor Jean Sibelius, from a humble explorer of Asia, Mannerheim 1940.”

Upstairs there are many books which belonged to Aino Sibelius and her daughters.

For example, there is a novel by W. Somerset Maugham which Jean Sibelius gave his wife as a Christmas present. One also notices Olavi Paavolainen’s The Cross and The Swastika, which Aino’s daughter Ruth had bought for her, and Adolf Hitler’s Mein Kampf, which the composer himself may have browsed through disapprovingly before he condemned the racial doctrines of the Nazis in his diary in September 1943. Over a hundred pages from the start of the book have been torn out.

Upstairs there are a large number of of children’s books and books on the history of Finland.