As slot games go, Slots Free Casino - House of Fun has a lot going for it. It's well put together, there are a lot of games to play, and it's got a sensible progression system.
The more you win, the more you level up, and the more machines you unlock. There are various different combinations of bets, spins, and ways of winning.
And if that's the sort of thing you want on your phone, you're going to get a lot of simple enjoyment out of this. It looks good, it's easy to understand, and it'll scratch that gambling itch.
But it's unlikely to convert anyone to the slightly odd free to play gambling genre, and while some will enjoy it, it's not going to stick around on their phones for very long.