This sounds very conterintuitive: For second language learners, reading popular smut books (such as Fifty Shades of Grey) may be better than reading high brow books (such as 1984 or David Copperfield), which is especially true for novice English readers.
The reasons I hold grudge against reading classics for language learning are multifolds. The most obvious one being: The vocabularies and expressions used in classical novels are oftentimes dated. If you were to converse with others in the style of Chales Dickens, your English will come off as archaic if not utterly confusing.
Secondly, Classics tend to be much more demanding books, which require readers to really apply themselves. If you are not born or trained later in life to be a somewhat ferocious reader in your native language, reading in your second language will only leave you with much higher mental pressure and frustration, and worse yet, it makes you associate English reading with those negative feelings and in the long run you lose your reading appetite.
This is where modern best sellers really shine: The vocabularies and expressions are much closer to being colloquial, which come in handy when you want to borrow them directly in your daily conversation. Furthermore, the story of those books are much more accessible and demand little from readers. Crime, Romance, Erotic, Whichever genre your poison may fall into, you have wide range of authors to choose from. Last but not least, being bestsellers, these books are addictive by nature, which is of critical importance for accumulating vocabularies for language learners.
For people grew up being told to read “good” books, reading Twilight or similar books might come off as a telltale sign of poor reading taste or intelectual laziness, but for second language learners you have to overcome this prejudice. I guess it is literally one man’s meat is another man’s poison, or the other way around.