The instruction below will show you the basic steps of how to make one single mkv from a Blu-ray Disc video without quality loss and also how to shrink it to a MKV, MP4 or AVI.
HandBrake (if you want to shrink the movie)
AnyDVDHD (may be required for some Blu-rays)
In MakeMKV choose the Blu-ray drive (If MakeMKV can't read the Blu-ray Disc, you might need to install AnyDVD HD and run in the background).
Just choose the main movie, the biggest title, keep one audio track (You can try to keep the AC3 DD audio track).
Save it by click on Make MKV. You need a lot of HDD space, around 10-20GB. This will take around one hour or so. (If MakeMKV can't read the Blu-ray Disc, you might need to install AnyDVD-HD and run in the background).
You can now play the mkv using for example VLC Media Player, KMPlayer or MPC-HC. Or play using Windows Media player with ffdshow and haali media splitter installed.
If you want to shrink the video you can easily use HandBrake.
In Handbrake load the mkv, Source->Video File.
Set output file.
Choose the High Profile->Film Preset (or use profiles for PS3, Xbox 360, etc)
Set the desired output file size, Under Video->Target size, like 8100MB for a dual layer DVD-R or 4400MB for standard DVD-R.