Why does he steal every year?
Horace Danby steals every year to fund his passion for collecting rare, expensive books. He loves these books deeply, but they are very costly, and his regular income as a lockmaker is not enough to afford them.
Each year, he meticulously plans a robbery and steals enough money to last for twelve months. He then secretly buys the books he loves through an agent. For example, during his robbery at Shotover Grange, he was motivated by the desire to buy three interesting books coming up for sale in the autumn. Therefore, his yearly thefts are entirely motivated by his urge to buy rare books.
Explanation
The textbook explicitly states that Horace Danby loved rare, expensive books, which is why he robbed a safe every year. He stole enough to last twelve months and secretly bought the books through an agent. This explains his motivation for stealing annually.