Sen. Scott Brown's (R-Mass.) minimum net worth decreased nearly 42 percent from 2010 to 2011, according to disclosure forms released Thursday.

The forms also show the freshman senator, who faces a tough reelection bid this year, received a $1 million advance on his memoir, Against All Odds.

In 2011, Brown received a $300,000 book advance, according to his personal disclosure forms. He had already received a $700,000 advance on his book in 2010 from Harper Collins Publishers.

The book "will receive payments (advance and royalties) that are usual and customary in terms and trade from Harper Collins," the form, which all lawmakers are required to file, states.

Brown's net worth fell from approximately $920,000 in 2010 to $535,000 in 2011, due partially to mortgages added to his filings this year. His liabilities increased from $115,000 to $450,000, and he disclosed at least two new mortgages totaling a minimum of $150,000 on a second home and a rental.

He also disclosed a $100,000 "equity line" on his primary residence incurred in 2002 that is worth a minimum of $100,000. Members were newly required to disclose personal mortgages this year.