Does he actually have a description of the subject matter? I haven't read Beautiful Evidence, but Tufte's descriptions of sparklines that I've read don't say anything about auto-generating sparklines in electronic documents based on data in the document, which is what is claimed in the patent. And claims 16-20 specifically cite embedding in a spreadsheet.
[Update] It seems he does, in fact. Tufte himself wrote a comment called "ET brief history of sparklines" on March 21, 2006 on this page: http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0...
"My first sparkline sketches were made some 15 years ago when I reviewed an HP medical interface for monitoring hospital patients (which involved, I recall, a Unix box for every ICU patient, or maybe a Unix box on a cart wheeled around the hospital). The idea was to put sparklines on the margin of a big spreadsheet recording all patient data (event by time), thereby summarizing the time-series history of each event category. My conclusion was that the medical staff would rarely look at the original spreadsheet and would instead just look down the column of sparklines showing the events time-series. And then the original medical event spreadsheet could then be down-screen if a user wanted details."
Under 35 U.S.C. 301, you may submit proof of prior art to the patent office for any patent. To quote:
"Any person at any time may cite to the Office in writing prior art consisting of patents or printed publications which that person believes to have a bearing on the patentability of any claim of a particular patent. If the person explains in writing the pertinency and manner of applying such prior art to at least one claim of the patent, the citation of such prior art and the explanation thereof will become a part of the official file of the patent. At the written request of the person citing the prior art, his or her identity will be excluded from the patent file and kept confidential."
In short, call the patent office, and tell them that you wish to submit prior art under 35 U.S.C. 301. Given that you have a published book with a clear description of the subject matter, it is a very strong case.
Alternatively, you could ignore it. It may not issue, and even if it does, it may not be defensible.