for anyone who might want actual numbers instead of the fictional 6 - 8 hours mentioned in the guide, i finished the campaign+mansion in 19 hours and finished the time trials in about 9 hours. so, roughly 28 hours for the full 1000. i used a guide for the collectibles but not for the puzzles. my in-game clock says about 8 hours, which is probably what the author of the guide went by for some reason.
the guide should probably say 25 - 30 hours.
also, 2 of the collectibles videos in the guide aren't complete. i can't remember the exact levels, but i think one was the first level of greece and the other was the second level of the lost island...but i'm not positive. each of those 2 videos was missing 1 collectible.
overall, i would recommend not playing this game if you want to get the achievements and have fun at the same time. constantly having to reload your last save is just a big pain.