You can download them all for free here:

https://www.myharvardclassics.com/categories/20120212

The Reading Guide at the bottom of the page is the best way to get into them, I think. It's a daily ~15/20 minute selection. Be aware, it's the book's page number that is referenced, not the .pdf's page number.

Very cool. I actually inherited the collection as part of my dad's library. It's almost complete, missing a few (Elizabethan dramas if I recall). My process has been to periodically pick out a volume and start reading, been doing that for years -- I'll check out the guide. May be time to introduce some methodology.