How much was that worth?

I remember toying with this site a few months ago, and it's not only educational, but a lot of fun. Have you ever wondered how much that book that five dollar book your great grandfather bought in 1955 would cost today (all things being equal)? Now you can. For example, I recently picked up a really old edition of the poetical works of William Cowper from 1924. It is so well preserved that the dustjacket/sleeve is still on, which bears the price 8s 6d, or 8 shillings and 6 pence (the book is so old this currency doesn't exist anymore). So, after punching in a few numbers, I discovered that, if I were to go back in time to 1924, I would have to pay 16.15 pounds, which is approximately worth 33 CAN dollars.
Similarly, a nice hardcover in the US in 1955 would cost around 5 dollars, which today would be worth approximately 35. Looks like books, at least hardcovers, have always hovered around that 30+ dollar range. I remember the days, not so long ago, when a penguin would cost about 5 bucks (without exaggeration, this was in 1993 or so). Penguin inexplicably has its own economy, and the same book today would cost about 12+ dollars. Sigh...