Immoral, yes, stealing is stealing.
However, technically plausible, no - inventions are not simply miraculous new things that suddenly spring forth, they're iterative of many things that came before them (or combinations there of); so if you were to steal an invention then you'd need to steal the decades or centuries that went into developing it.
Could you jump twenty years into the future and steal Intels latest processor design, sure, but it's going to be no good without the 3nm fabrication required to make it.
Fashion and literature are even more fickle, fashion is a reflection of current trends, you steal an idea from the future and all likelihood is it will sink as it's not what's in. Literature is also a reflection of the now (at least the popular, high selling literature) - someone above mentioned Tolkien, Lord of the Rings is his lament on industrialization, which is very representative of the time and part of what makes it a masterpiece, without which, there's a chance you wouldn't end up with the riches you presumably seek from such time travelling shenanigans.
Really you should just get the sports almanac or lottery numbers, it's a much more reliable method to be knee deep in private beaches, blow and hoes.