I went looking for information about the original post. Going that the OP said the book is a "bpp acca ebook", I did a quick Google search and then looked on the
About BPP eBooks and wandered in the FAQs section. According to them, the only download for offline reading is using the Android or iOS apps. On Windows/Mac/whatever else, the only access is online.
To quote a couple of lines from the FAQs:
Can I print my eBook?
No, there is no printing capability available for our eBooks.
________________________________________
Can I download the eBook as a PDF or use it outside of the app?
No, the content is protected and will remain within the app.
Which makes it appear that the OP has copied the folder the ebook was downloaded into on his phone/tablet to his computer and now wants to make an illegal copy that will violate the 18 months access to the ebook from time of reception of the confirmation email.
Give the ACCA courses are for accountants, I'd have to ask myself if I really want an accountant who is willing to publicly ask for help on pirating an ebook to be doing any work for me.