You will have to use the Cosine functions to get the output in Angles. (Direction Cosines)
You may read more about it here: Starlino - IMU Guide
(Just before Part 2. Gyroscope starts)
The datasheet of ADXL345
mentions changes in Output Resolution with Changes in g-force. Look at Page 4 -> Under Specifications -> Row 2 -> Output Resolution may go up to 13-bits at high g-forces (16 g's).
Also, on Page 27, FULL-RES bit is mentioned. Here is an excerpt:
When this bit is set to a value of 1, the device is in full resolution mode, where the output resolution increases with the g range set by the range bits to maintain a 4 mg/LSB scale factor. When the FULL_RES bit is set to 0, the device is in 10-bit mode, and the range bits determine the maximum g range and scale factor.