Most of earnings came from book sales, as Obama family discloses assets of $7.7m and charitable donations of $329,000

It used to be that American presidents served their terms, wrote the book and hoped to rake in the royalties. George Bush is working on his now – although it should be noted his wife, Laura, has beaten him to the bestseller list with her new tome.

But, as ever, Barack Obama is different. He wrote the book – two of them, in fact – and then became president, earning himself a lot of money last year.

The president reported income of $5.5m (£3.8m) last year on his tax returns, most of it from Dreams from My Father and Audacity of Hope, his two bestselling books that have continued to be popular, proving that in contrast to the track record of presidential accounts, Obama can both write and has something to say.

According to the White House financial disclosure forms, the Obamas declared assets of $7.7m, not including the family home in Chicago. But the assets do include the family dog, Bo, who is valued at $1,600 and filed under "gifts, reimbursements, and travel expenses". The Portuguese water dog was a present from the late Senator Edward Kennedy.

Obama declared his Nobel medal and diploma (recorded as "value not readily ascertainable"). The $1.4m cheque he collected in Oslo last December was donated to charity. The Obamas also donated a total of $329,100 to 40 different charities including the United Negro College Fund and the aid agency, Care.

The president's other declared gifts include $500 in travel expenses from the National Association of Rock Collectors to attend its conference and a $300 leather briefcase from a Frank Jones of San Francisco, who is recorded asa "personal friend".

The Obamas also have some retirement savings accounts and college savings for their daughters, Malia, 11, and Sasha, eight. Most of the book income is invested in US treasury bills.

Five days before he was sworn in as president, Obama received a $500,000 advance from his publisher. The declaration records that he makes 15% of the hardcover sale price in the US and up to 10% on paperbacks. Obama's income from his books far outpaces his annual presidential salary of $400,000 which met only a fraction of the Obamas joint income tax bill of nearly $2m.

The vice-president, Joe Biden, did not do nearly so well. The Bidens reported income last year was $333,182.

But he did get some unique gifts including a 1928 first edition of James Joyce's Anna Livia Plurabelle, signed by the author and valued at $3,500.

Margaret Spanel, a 97 year old widow from New Jersey, gave Biden the book after watching him make a campaign speech in which he said that Joyce was his favourite poet.