It says that when I purchase a bond with accrued interest, I should record it as follows:

Dr Bond (asset)
Dr Accrued bond interest (income)

Dr Bond (asset) 1,000
Dr Interest (income) 10

This results in $10 of negative income at the time of the purchase.

You're right, the bond interest payment has to be received before year-end (or the date of the financial statement) for proper reporting. If it isn't, then you need to make an accrual as follows:

Dr. Accrued Interest (asset: Accounts Receivable) $10
Cr. Interest (income) $10

Then record a reversing entry in the first month of the new year, putting the "negative income" back in the books. When the bond interest of $40 is finally received, the "negative income" will be wiped out, and income will be reported as $40 minus $10 = $30.