Apparently the KryoFlux adapter will give you a floppy controller to USB. This means that since modern motherboards (e.g. Intel socket 1155) do not have floppy controllers, or older (e.g. Intel socket 775) have it but don't support 5.25" drives or support a single floppy, now we can actually have up to two floppy drives of any kind (PC, MAC, Amiga, Commodore, etc.).
As far as I understand with that adapter you get the needed floppy controller. Then you need an appropriate floppy cable to connect your 5.25" drive (thank God, I have kept one or two, it's nearly impossible to find one today). You will probably also have to connect the drive with a power source (mine takes the standard Molex, so no problem even for a modern power supply). Then if everything goes OK, the drive should appear as
A: in My Computer, or at least you can access it using KryoFlux's software.
As they claim, you can read and write to the drive, so not only can you backup all your old floppies, you can use them for (very small) file transfer. Unfortunately, a 5.25" PC disk is only 360 KB (single sided, double density) or at most 1.2 MB (single sided, high density) so there is not much use by today's standards. Needless to say that to access a 1.2 MB disk you need a high density 5.25" drive, while a 360KB disk can be accessed by either a high density or double density 5.25" drive.
So I would look no further, I would go for the Kryoflux solution if I had too many floppies to read. Another solution is to use an older computer that can accept the old drive without any adapters. Backup all your disks to another medium (CD or USB, etc.) and then you shouldn't need the drive anymore, since the disk capacity is TOO small by today's standards and it is useless to use these disks for saving data.
Since we are talking about a 5.25" drive, most data (and games, programs, etc.) in it must probably be from MS-DOS era, so you can use them in DOSBox emulator. It works perfectly even in 64-bit Windows! There is even a way to install Windows 95 in a virtual disk if it happens to have any old Windows game you want to play in 64-bit Windows. Of course the game must play in Windows 95; if you need newer Windows version try Compatibility Mode on your host Windows system or use a better virtual PC application such as VMWare.