Product liability laws can vary from one state to the next, but typically, the manufacturer of the product is responsible for injuries caused by the product. A person who has been injured by a defective product may be able to sue the manufacturer or distributor of the product for damages. However, in order to do so, that person generally must have read and followed the instructions in the user manual. If they did not read and follow the instructions, they are not eligible to sue for damages.
That said, product liability is a very complicated area of law and It would be advisable to speak with a lawyer before giving up on your case. For instance, if the product is intuitive and doesn't usually require reading instructions to operate in a normal fashion, this could allow one to sue even without reading the instructions.