Books can be attributed to "Anonymous" for several reasons:
* They are officially published under that name * They are traditional stories not attributed to a specific author * They are religious texts not generally attributed to a specific author
Books whose authorship is merely uncertain should be attributed to Unknown.
Bhagavad Gita is excellent, but I struggled with the Edwin Arnold's translation. It is in a high register and uses a lot of antiquated language. Still worth reading, especially if it's free.