1) Book of Monsters is one that has been reprinted many times. The original Little Soldier books have different covers so easy to see which edition you have (there might be a couple different prints in there too but no real change to content):
http://tomeoftreasures.com/forum/viewtopic.php?t=355Also, later reprinted by Gamescience (with at least 2 different printings);
http://tomeoftreasures.com/forum/viewtopic.php?t=682Also included in The Fantasy Gamer's Compendium by Gamescience (with at least 3 different printings):
http://tomeoftreasures.com/forum/viewtopic.php?t=8062) Never seen any sign that Book of Terror was published
3) Yes there are some multiple printings of some of these - I would have to dig these out to go through them again.
Some different printings are listed on ToT (I think there are a bunch more though):
http://tomeoftreasures.com/forum/viewforum.php?f=144) The Little Soldier books tend to go in the $40-$65 range, The Gamescience Book of Monsters are harder to find and also sell in the $40-$65 range. Fantasy Gamer's Compendium are usually $25ish - the white one is very difficult to find so it would sell higher to collector's looking to complete a set.