For all Gimli was included in the book I still did not learn enough about the real h im, the depth of him to satisfy me.
To understand a Dwarf, you'd have to be a Dwarf yourself, as even more than Elves they usually keep to themselves and never leave their mountain realms or underground halls, safe to trade some of their goods.
The Free Peoples of Middle-earth knew only a few words in Dwarven language ("Khâzad" being one of them) and hardly knew anything of the Dwarves' origins and beliefs (which is why there are a lot of tales about their afterlife, like that they would turn to stone, etc).
It seems that the information about the Dwarves in the Appendices, may all have been revealed by Gimli himself to the writer of it (I believe that section was part of Red Book of the Westmark), for instance it was Gimli who partly revealed the mystery of Dwarven women - he named Dís as being Thorin's sister.
Lucky though, that Tolkien's dwarves are benevolent, unlike the original Dwarves of Nidavellir from Nordic mythology, who are sly and cunning and whose crafts tend to cause their buyers quite some harm.
Give up the Halfring, she-elf...