No, info on the Middle Ages is most definitely not sparser than on antiquity. However, because it is so much more, there isn't as concentrated a group of places to find lots of information on them. And additionally, I don't think academic medievalists have been as good at establishing a popular online presence as classicists.

That said!

By way of primary sources, you mentioned two ancient authors who wrote histories. A couple of great medieval historians available in English translation:

• Jean Froissart Chronicles - on the Hundred Years' War, chivalry, 14th cent. France, etc
• Orderic Vitalis, The Ecclesiastical History of England and Normandy - classic medieval historiography, starting with the Bible and going up through the present. All 4 volumes of English translation online; I'd start with II, III, or IV. There's some good stuff in I, but a lot of it is Bible retread and popes. The good stories are post-Norman Conquest. ;)
• Usama ibn Munqidh's Chronicle of the First Crusade/Crusader states available, online as An Arab-Syrian Gentleman and Warrior in the Period of the Crusades

You also might want to check out:

• The Travels of Marco Polo - Penguin Classics translation is great if you want to pay, but you can find older ones of this online for free as well. You'll recognize some of the anecdotes told by Herodotus in here!

As for modern books, here are some favorites that require almost zero background knowledge (helps if you've seen enough movies about the Middle Ages to know what a knight is, haha)

• Barbara Hanawalt, Growing Up in Medieval London
• Jeffrey Singman, The Middle Ages: Everyday Life in Medieval Europe
• Eric Jager, Blood Royal - basically CSI: Medieval Paris
• Frances and Joseph Gies, Cathedral, Forge and Waterwheel - technology and invention in the Middle Ages
• Ruth Mazo Karras, Sexuality in Medieval Europe: Doing Unto Others

Hope this gives you a solid place to start!

If you subscribe to audible, you can access ‘the great courses’, series of lectures by leading professors on their area of expertise. The lectures on the Middle Ages are excellent. They are each 30 minutes long and the Professor summarises what he’s saying/said at the beginning and end of each lecture. (Making it easier to recall) There are accompanying lecture notes you can download for free with the course. My only caution is that after you start using these courses you may find conventional history books a bit ‘light’. The amount of info covered in each course is significant

I recommend giving Nigel Bryant's translations of The History of William Marshal and The True Chronicles of Jean le Bel a read. Both are highly entertaining and informative texts. Philip Augustus referring to the traitorous nobility he had won away from King John as "shit rags" always makes me laugh, and le Bel was Froissart's model for recording deeds of daring do. Philippe de Commynes' Memoirs is also quite enjoyable.

For modern authors, Sun has already snagged most of the good recommendations, but I suggest reading both volumes of David Nicolle's Medieval Warfare Source Book, Joseph and Frances Gies' Merchants and Moneymen (which uses the lives of real people to explore the medieval economy) and Chris Wickham's Medieval Europe.