Sometimes when it doesn't seem to getting off to a very fast start, I throw in some bark. Much of my firewood is oak, and the bark usually detaches as it dries. A lot of hardwoods are that way. It burns extremely well. It very reliably improves the burn.
In the picture above, the intensely burning area is a few small slabs of bark, with a sweetgum log on top.
This is a closer view. Oak bark does not burn for long, but it's not a flash in the pan. It burns long enough to get split wood (or an unsplit small piece) burning aggressively. Throwing several sheets of bark into the stove at once heats the stove up to about 400 fairly readily (stove top temperature). Although 400 might seem low, the max is about 600 and soapstone stoves seldom get above about 350-400).
Bark also functions well as kindling.
All of this may sound counter-intuitive, and some people dismiss it as being useful, because bark resists flame. This is definitely true for small pieces that I throw into the stove with bark intact: the fire has to be going somewhat well for that to work. It takes a few minutes to burn through the bark and get to the wood underneath. However, when off the original wood (split or otherwise), the bark by itself does burn well. Contrary to what a lot of people have indicated, I haven't noticed that it leaves more ash. It may...but I never use enough for that to be apparent. I have never fed a fire nothing but bark, although I have enough of it that it could be done.
Oaks have good bark and some other hardwoods do. Wood like cherry and peach has very little usable bark, but it burns okay, too; it's just paper-thin. Southern pines don't have too much bark to them, and it often doesn't seem to separate, but western pines sometimes do: ponderosa pines can have very thick bark, and very old douglas firs can have bark up to 14 inches thick (though trees of that size aren't likely to be often used for firewood).
Bark works. It's a reliable go-to.