Since you mentioned Lost Mines of Phandelver, I thought I'd point to a notable rework of the campaign which incorporates LMoP.
A fellow from the ToD subreddit did a rework of Tyranny of Dragons, with Lost Mines of Phandelver as an introductory scenario leading into starting ToD from level 5. He released 2 DMs Guild products for a Hoard of the Dragon Queen rework and a Rise of Tiamat rework. They may be worth checking out if you don't mind spending another $10
Managed to play Arkham Horror twice in one week, though missed playing War of the Ring with my partner.
Wednesday was an 11 hour Arkham Horror marathon due to 2 friends moving away. Four of us took the day off. We attempted the two-party Dream Eaters campaign with two groups of 3. The awake team blitzed through their scenarios while the dreamers struggled through theirs (having already played the other way, the dream scenarios are more complex). This resulted in the awake team waiting 30 mins - 1 hour per scenario for the dreamers to finish. We finished at the end of scenario 3 as we were so exhausted.
Saturday was my Path to Carcosa group, which proved to be a lot more fun, probably because we weren't trying to cram a whole campaign into one day. Completed scenario 3 before the final agenda came up. Our seeker is ridiculous at hoovering clues.
Ah, you too run Call of Cthulhu?
I'm running an in-person Quest for the Frozen Flame campaign with Foundry for maps/bestiary. They're about to come to Rimecrag Pass tomorrow. I did have an oracle ready for Strength of Thousands but that fell through in the planning stage.
People have already mentioned my two suggestions: 4E DMG2 and The Lazy Dungeon Master.
This isn't a specific book recommendation, but I would recommend reading a diverse range of RPG books, across a breadth of topics which interest you. In particular, reading the storytelling sections and how those guidelines interact with the delivery mechanics of the specific game can offer a new perspective on how to run your games.
For example, I enjoy horror roleplaying in particular, so books I may read are Call of Cthulhu for Cosmic Horror or the World of Darkness/Chronicles of Darkness books for Personal Horror. While I run Call of Cthulhu a lot more than World of Darkness, the tips on storytelling personal conflict from WoD offer some interesting insight into running sanity conflicts in CoC.
I use Foundry on an Oracle Always Free server. I project that in our department's meeting room from the room's computer; I then run the GM side and music from my laptop.
At the university I run Halloween sessions for new players, and by far the best scenario I've run is the first one: House of the Midnight Violet. It's a 3 hour scenario for a party of 4th level. I've run it twice for a party of 3rd level with no adjustments. It's plays very well as is, though I'd personally suggest running the groups of dolls and cats as swarm creatures rather than individual creatures, for the sake of your own sanity.