Delta SkyMiles members can earn 10,000 bonus miles for subscribing to the getAbstract book summary service. The service provides unlimited access to in-depth summaries of leading best-selling business books, which you can read, download and listen to whenever you want. Summaries are offered in PDF, Palm and MS reader formats. Each book summary is condensed to five pages and includes the book’s key ideas that can be read in less than 10 minutes.

The company offers over 4,000 summaries and 500 new books are added each year. You can purchase a Gold subscription for $299 per year and receive 10,000 miles — half-year Gold subscriptions are available for $179 but miles are only offered for a full-year subscription. At $2.99 cents per mile, the mileage offer is only slightly more expensive than buying miles from Delta at 2.75 cents per mile.