Difference between OCR A and OCR B? (A Level) Watch
OCR A follows a pathway looking at in depth statistical analysis, whereas OCR B is pure mathematics (algebra, mechanics, simple statistics). Although OCR A still have concepts of pure maths and mechanics in it for the purposes of statistical analysis.
In short, the OCR B textbook will help you with some of the basics for OCR A but you won’t be able to rely wholly on it - it’s a good starting point.