It's one of the blue ornamental sages, most but not all of which are perennials. If you want to try to figure out exactly which one I could go on a comparing-to-book-photos expedition, or you could try that yourself by googling "blue sage" or something like that.
Hope this helps,
Pat, quite fond of perennial blue sages - pretty, bloom all summer with just a wee bit of deadheading occasionally, don't need watering, and you can't kill 'em with a stick
Specifically that looks like a form of Salvia nemorosa, meadow or field sage. They reseed readily, bloom for a long period of time if deadheaded, and are generally a delightful addition to the garden. More about them here.