Beck

I’d like to buy some hard-to-find technical books from the USA, for personal use. The seller has told me that as books the package will be VAT exempt, which looks right but I’m finding it very hard to find a definitive answer. Is that correct? Also - the total cost is around the crucial £135 amount, depending on the current exchange rate. If over £135, would I still be liable for import duty, whether or not the items are VAT exempt? Any help or advice gratefully received