The latest release is a 70-80MB download (depending on archive type). Where are you getting 300MB from? The uncompressed size?
It's amazing that people on StackOverflow suggest using this package for things as simple as sort functions.
If you're using any kind of sane package manager for your builds - NuGet on Win32, distro-specific package managers on Unix etc - that's exactly how it is presented. So you don't take a dependency on Boost - you take a dependency on boost-filesystem, or boost-regex, or boost-date_time etc.