KDP (or Amazon Print on Demand for books, if you preffer) book sizes extracted from their File Setup Calculator (v5) as of today, 20200418:

incm
5,00 × 8,0012,70 × 20,32
5,06 × 7,8112,85 × 19,84
5,25 × 8,0013,34 × 20,32
5,50 × 8,5013,97 × 21,59
6,00 × 9,0015,24 × 22,86
6,14 × 9,2115,60 × 23,39
6,69 × 9,6116,99 × 24,41
7,00 ×10,0017,78 × 25,40
7,44 × 9,6918,90 × 24,61
7,50 × 9,2519,05 × 23,50
8,00 ×10,0020,32 × 25,40
8,25 × 6,0020,96 × 15,24
8,25 × 8,2520,96 × 20,96
8,50 × 8,5021,59 × 21,59
8,50 ×11,0021,59 × 27,94
8,27 ×11,6921,01 × 29,69

If you need a quick view, you can download the following poster that can be printed on a a3 paper size:

amazon print on demand book sizes