I rarely buy guides but did in the past simply because I found the guides to be cool looking and just...well...cool
The last guides I bought:
Dragon Age Origins Hardcover (used at first to optimise Tactics)
Fallout New Vegas Hardcover (just looked at it just to see what were the cool unique weapons)
Skyrim no Hardcover (looked at the items available and was disappointed with the lack of cool uniques

)
I just like the look of Harcover guides but I rarely use them. So I might not buy anymore guides from now on.