The bonus to a fantasy sleeper on a terrible Astros team? For one thing, despite having only 57 major league games under his belt, Altuve should bat second, giving him a chance to score more runs. Even the Astros score runs sometimes, you know.
Another bonus to a less than stellar Astros offense? These runs they sometimes score have to come from somewhere and it's likely the speedy Altuve will be expected to put up a lot of stolen bases to produce them.
Perhaps Altuve's biggest strength is his ability to hit for average. He hit a .361 in Double-A and it it not unreasonable to assume he will hit between .280 and .300 this year. He is a contact hitter and his strikeouts are infrequent, putting him at an advantage in the RBI category as well as average and on-base percentage.
Despite being of smaller stature, he has some power in his swing and could potentially hit 10 home runs this season.
You might be able to find better second baseman, but in deeper leagues, he is an excellent option. Not a bad backup second baseman either should you find him available in later rounds.