hi there
i applied for economics (and maths joint honours degree) in september and only took econ at as level but found it really interesting so i read a lot of economics book over the summer of year 12! some i enjoyed were predictably irrational, dead aid, the undercover economist, narconomics, seriously curious (the economics explains) and doughnut economics (this one was my favourite) though i wouldn't read all of them just for your personal statement; you don't need to mention that many books (i most certainly didn't!), i just read so many as i read a lot and found them really interesting
in general though, if you want to get an understanding of econ, i'd either read doughnut economics (which is a nice introductory book imo) or do an online course in econ (there are lots of free MOOCs on websites like the open university, i'd give them a google
) or look on youtube (there are quite a few great econ channels on there!). there are also quite a few fairly accessible econ podcasts: planet money, freakonomics and more or less: behind the stats are the ones that i can think of off the top of my head
best of luck with it!