Frustratingly, you can't get the kindle version if you live in the UK (I actually live in the Netherlands, which Amazon doesn't operate in at all, but my account is from the UK). The kindle version even shows up on the US site until I log in.
EDIT: I tried to use Amazon.nl (they do have a kindle store, just not regular Amazon), they have the kindle version of the book but when I log in after buying it I'm told it's not available in my country
I use the app "Headspace" as a meditation beginner. The monthly price after the first 10 sessions is a little steep (can't remember the exact price) but there's a lot of extremely high-quality content covering mindfulness in almost every aspect of life. I think it's worth the price.
I have lots of respect for spiritual people and adherents to both religious and non-religious supernatural practices, but I can't pretend that the association with supernatural beliefs didn't put me off getting into meditation and yoga for a long time, despite the very real empirical benefits. I understand that for you these beliefs (which, whether they are true or not, are not scientifically proven, which is important for me) increase the benefit you get from meditation, but for the non-spiritual these associations are a barrier to entry that must be overcome. I now meditate regularly and love it, but I still have some measure of resistance to yoga.