While not a systematic argument (either exegetically or metaphysically) for orthodox/evangelical Christian universalism, these two texts (or four, strictly speaking ) are absolutely essential for any modern reference to this school of thought. Besides, they’re also chocked full of amazingly good devotional theology; in fact, the universalistic/anti-gnostic content would constitute less than 1/5 of the material (by a loose reckoning where I wrote down a bunch of numbers until I came up with one that sounded right. ) Fans and students of C. S. Lewis owe it to themselves to read these as well (even though Lewis never ended up a universalist).
To put it shortly, there are excellent reasons why “Gregory” chose “MacDonald” as his pseudonym.
The following two links go to two relatively modern publications of these works on Amazon.
One American publisher, however, has been printing MacD’s work in beautiful and reasonably priced hardback greencloth volumes for years; and this is where I got my own copies: Johannesen Printing & Publishing As a bonus, their binding of Hope of the Gospel includes The Miracles of Our Lord, which directly inspired the culminating chapters of Lewis’ crowning apologetic work Miracles: A Preliminary Study.
Johannesen also provides free-use html pages of all of MacD’s works (including the titles discussed here), though personally I suspect better versions can be found online elsewhere. (MacD’s works are public domain now, I think.)