Llama adventure was the first text adventure/interactive fiction I played all the way through, and was the game that really got me interested in IF. I found it easy to work with, the puzzles were interesting but not extremely hard, and the humour was quite good.
When I came back to Llama Adventure after playing more text games and getting acquainted with the standard commands and such, I actually found Llama Adventure harder to work with, because it wouldn't accept commands such as "examine" (you have to use "look at" instead), and there were some cases where you have to try to figure out a specific wording such as (Spoiler - click to show) "use badkey with lock" because other wordings such as "unlock door with badkey" doesn't work.
So if you're new to IF, this is a great introduction! I showed it to a friend recently and she loved it (started playing other games by the author in order to get the extra codes for Llama Adventure). If you're more experienced with IF, it can get a bit frustrating.