If you do not care about reading English interviews, the Japanese edition ( 鉄コン筋クリート アートブック ) is often cheaper ($80-120) than the English edition. You can buy it from proxy services like Buyee or Mandarake. Once you own the physical book, scanning it for personal use (a personal PDF backup) is generally considered fair use.
The visual world of Tekkonkinkreet is split into three primary volumes, each focusing on a different layer of the film's production:
Catalogue