These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.00 s (backtrack: 0/20).

[ebuild  N     ] app-text/mdbook-0.5.3::gentoo  USE="-debug -doc" 9139 KiB

Total: 1 package (1 new), Size of downloads: 9139 KiB