Basic differences between 'commercial' and literary translation

There are several major differences between literary work and commercial translation activity.

Time Frame: While commercial work comes with days-away or even hours-away deadlines, book translation can have an open deadline, so that you can take as long as you like, within reason. Obviously, you want to finish your work as soon as possible, and the author is also eager to make the book available to the publishing world. Having all the time you need allows you to proceed at a comfortable pace. You should be able to work about five hours a day, with breaks. It is necessary to give yourself plenty of breathing time, especially between writing and revision, in order to gain a fresh perspective.

Monetary Considerations: Different arrangements for literary translations are usually followed, including 'pay for services' involving a set amount for the translation, which then could require complete ceding of rights upon completion. Another would be a royalty arrangement, with an advance or a guaranteed minimum.* In the latter scenario, if the book is a success, the translator could have long-term income, which could well exceed a per-word rate or set price for the work. This is a matter of negotiation, and depends on what the translator sees as his long-term prospects. Although most people have little taste for gambling on the long-term and would much rather walk away with a check.

Relations with the Client: Work coming through an agency usually involves virtually no contact with the original client. Some agencies are not very good about getting helpful information from their clients. This often means that the translator has to go to industry or actual client websites seeking terminology, descriptions of industrial processes, and perhaps other translations on the same topic.
In translating a literary work by a living author, there is the very real possibility of close contact with that author. Purposely avoid consulting existing translations of the work; although they may help untangle questionable syntax and time references, it is preferable to avoid “contamination” from another translator’s interpretation. 
Obviously, doing a job by a dead author would not afford the same opportunity, but in such cases there may be ​prior translations, or translations into other languages that can be very helpful, as well as other critical literature. 

Psychological Approach to the Work: With literary translation, unlike most commercial work, one develops an important psychological relationship with the project, the subject of the book, and the author. One grows either to love the work or to despise it. 

Extract from: 'On Becoming a Literary Translator' by John B. Jensen

Notes:
*Landers, Clifford E. Literary Translation: A Practical Guide (Cleve don, Buffalo, Toronto, Sydney: Multilingual Matters Ltd., 2001), 191-195.