Yes, that's it. The boot.iso is supposed to boot the machine with modules needed to access the network and do the ftp install. But notice that you won't have isos of the other cd's, as this type of installation does not relies on cd's, but on the packages.
The system will boot, do some testings and then let you choose the closest mirror. From this point, you'll download countless amounts of packages. Must have a good link for this to run smoothly.
But you can download the entire tree and build a volume for installing in aonther computer on your network, if its the case. Total is ~3GB of data.