Rip off a page each day and learn a new phrase. I was given one of these for 2006 and found it an enjoyable way to study. My skill at German improved slightly during 2006, and though this was not my only study tool I think the quick, regular practise it encourages is good.
The level is variable, from the most basic phrases to proverbs and obscure vocabulary. Assuming the format is the same as 2006, weekends are done as a single page, and some pages do not have a phrase but instead a bio of someone famous born on that day. The Amazon data lists it as 640 pages. Printing is only on one side of the paper, so I imagine the correct figure is 320 pages.
At 5000 yen on Amazon Japan it is more expensive than I realized. The Amazon UK price of £9.99 (i.e. around 2000 yen) seems more what I would expect, and at that price I think it is a good buy.
See if it is any cheaper yet at Amazon Japan, or buy it at Amazon UK here.