If you want the closest thing to more Cornwell
Bernard Cornwell, the rest of it.
Start with the Grail Quest trilogy, because it is the Hundred Years War and it is Cornwell at full stretch: Harlequin taught half of us what this war feels like from underneath an arrow storm. Sharpe is worth your years, but go in publication order and know that the later prequels are the engine running with the fire banked. The book of his I'd press on you last is the odd one: the Warlord Chronicles is the best prose he ever wrote, stranger and sadder than anything with Sharpe in it. If you are rationing, skip the post-2006 Sharpe and you will miss less than you fear.
If you want accuracy you can check
Christian Cameron.
The Long War books are the way in: Killer of Men first, marathon runners and Persian cavalry and the ground-level truth of a spear line. The fighting reads right because the man can fight (trained historian, re-enactor, fencer), and readers cite that constantly, which makes him the standing proof of this page's whole theory: trust comes from credentials you can check, never from the word "authentic" on a cover. Fair warning: the casts are big and he will make you keep up.
If you want the Hundred Years War specifically
Dan Jones, the Essex Dogs trilogy.
The Essex Dogs books are the closest thing on this list to what I write, same war, one decade earlier, same ground-level altitude, so read this verdict with that in view. The mud is real, the research is a working historian's, and the company of ordinary soldiers is drawn with genuine love. The honest caveat: the dialogue sounds modern, and readers split hard on exactly that point. Both halves of that split are right. You will know within three chapters which half you are in, and the first book is the cheapest way to find out.
If you want it grittier
Robert Low, the Oathsworn books.
Starting with The Whale Road. Viking age, first person, a band of oath-bound men held together by bad luck and worse decisions, and the prose has gravel in it. This is the one for the reader who thought Uhtred was too courteous.
And one of them is mine
Greg Steinig, The Man Who Died at Poitiers.
Mine is the 1355 chevauchée told from the baggage train: a pressed engineer who builds the machines and counts the fodder, in an army burning France on purpose. The route is the real one and the sources are named on this site, because I wanted you to be able to check me. What it is not: it is not a glory story, and it is not gentle. Towns burn and the book does not look away, so if you want your medieval war kept at a comfortable distance, skip this one. There is also one thing about the man telling it that I will not spoil, except to say the title is literal. The opening chapters are free below. Decide from those.