My very own book, published by The Crowood Press, that contains pretty much everything you need to know to confidently make fermented foods at home: we cover making milk kefir, water kefir, kombucha, and also veggie ferments like sauerkraut, chilli sauce, and my popular kimchi. The book also covers recent research into links between the gut microbiota and fermented foods.
PS watch this space I’ve written another one - same publisher - all about making vinegar. It will be published in March 2024.
You might like to purchase the e version instead, in which case please visit the Crowood Website:
https://www.crowood.com/products/fermented-foods-by-caroline-gilmartin
And if you have an Amazon Prime account, it might make more sense for you to order it from them (for all the downsides of Amazon, those reviews really do help - this is an affiliate link I will receive a few pence from Amazon - this will not affect the price you pay).