If you have yet to purchase any books on the Windows Store, now is a good time to explore the new digital store category. Indeed, Microsoft is running a limited time offer that will grant you $5 Windows Store credit for any book purchase in the Windows Store (via Neowin).
— Windows Store (@windowsstore) June 23, 2017
This is a pretty good deal, as you'll get the $5 promotional gift code even if you purchase a $0.99 book in the Store. The special offer is only available in the US through June 30, you'll need a PC or phone with the Windows 10 Creators Update to take advantage of it (eBooks are not available in the Windows Store with prior versions of Windows 10). Sound off in the comments if you're likely to take advantage of this offer this week.