This book looks great, and really fills your mind with the feeling of the subject matter (the honobono/fantasy anime atmosphere). The artwork ranges from adorable sketches to gorgeous, and really inspire.
The overall theme of the game, that of a series of journies between small fantasy towns by "normal" sorts of fantasy characters is novel in a market full of either high gonzo fantasy or grim and bloody sword and sorcerery. Nature plays a large role in the theme of this game and overall I think it achieves the "Miyazaki's Oregan Trail" nickname it is often given.
I wouldn't call it "rules light" so much as being in the bottom range of "medium". It's got some crunch to it, though all rolls are always made by combining two skills (or one skill rolled twice together) and so should be easy for anyone to pick up. The gathering, crafting, camping, animal, and other such rules makes the journey itself the main thing a given session should be about. Combat for me is a little too simple, being abstracted with a front and back line (ala Final Fantasy) and 5-10 objects on the battlefield that can be used by anyone to help their fighting rolls. For me combat is the weakest part of the ruleset, it's not very exciting. I think that might be the point, however, as combat is implicitly not the main focus of the rules or the game. (Running this game, however, I plan on using a grid mat to try and achieve a Final Fantasy Tactics feeling).
The journey rules are really interesting and require a good amount of improv for the GM. I wish the book had come with tables, perhaps in appendix form, for some example hazards in each terrain type to help newer GMs out (or GMs that need some inspiration).
The idea of a built in DMPC that helps the party as a sort of helping (or maybe even trickster) spirit is refreshing and fun. The fact that there are options like items to equip your dragon spirit with that change how the rules work is super fun and exciting.
Overall I like the rules and think they support the kind of game Ryuutama tries to be.
The rulebook is set up well, beginning right off with a short summary of the game and it's rules, followed by character creation, and continuing with detailing out everything. I see no problem with it's formatting or usability.
I am excited to both try this game and to pillage it for ideas to use in other games. I really think the overall way the travel and crafting is done would work well in D&D 5e, for instance. I recommend buying this if you are at all interested in: anime/manga, a less violent sort of game, the fun of the journey itself, nature, or cat goblins.