Here is a guide to the qualities of different woods for burning.  It is always a good idea to ask your supplier what sort of logs they are selling. As you will read, some are a lot better than others:

Alder: a softwood with a high water content.  It gives out little heat and doesn't last for long.

Apple: a hardwood that bums slowly and steadily when dry, with little flame, giving good heat. The scent is pleasant.

Ash: a hardwood that is considered the best for burning; it gives out a good flame and heat, and will bum when green, however it is never a good idea to burn green wood in a stove.

Beech: considered a rival to ash, though not a close one. It does tend to spit out embers far into the room, so beware using in an open fire, but ideal for a stove.

Birch:  a hardwood that produces a good heat but it burns quickly. The smell is pleasant.

Cedar:  a softwood that burns well when dry. Much better in a stove than in an open fireplace.

Cherry:  another hardwood that burns slowly, giving out good heat.  It also gives off a nice smell when burnt.

Chestnut: this must be one of the noisiest firewoods, best in a stove.  It has a small flame and doesn't give out much heat.  Avoid if possible, or mix these logs with a hardwood. 

Douglas Fir: not much good.

Elder: a softwood that is very smokey. It is a quick burner, without much heat.

Elm: this is commonly offered for sale due to Dutch Elm disease. To bum well it needs to be kept for two years. Even then it will smoke. Vary variable fuel.

Hazel: good.

Holly: good, best seasoned for a year, like all logs for woodburning stoves.

Hornbeam: almost as good as beech.

Laburnum: one to avoid because it is a  poisonous tree, giving acrid smoke, tainting food and best never used. However it can be used by wood turners as it has a beautiful pattern.

Larch: a softwood that gives a crackly sound.  It gives out a scent, and is quite good for heat.

Laurel: gives a good bright flame.

Lime: not a favourite as it has a poor flame.

Maple: another hardwood that is good for burning.

Oak:  a hardwood, it gives out few flames and the smoke is acrid. Dry old oak is excellent for heat, burning slowly and steadily.

Pear:  a hardwood giving good heat scent.

Pine: is a softwood that bums with a good flame, but it is apt to spit. The resinous Weymouth pine has a lovely scent and an interesting blue flame.

Plane: burns fairly well, but is prown to throwing sparks.

Plum: hardwood that gives heat and scent.

Poplar: one to avoid.

Rhododendron: the thick old stems, being very tough, burn well.

Robinia (Acacia): burns slowly, with good heat, but with acrid smoke, so use in a woodburner.

Spruce: another softwood that burns very quickly and gives out a lot of sparks - one to avoid if possible.

Sycamore: burns with a good flame, with moderate heat. 

Thorn: one of the best woods. It burns slowly, giving a good heat and not much smoke.

Walnut: hardwood that gives out very good heat and a beautiful aroma.

Willow: Poor as it has a high water content. It must be dry to use, and then it burns slowly, with little flame. Apt to spark.

Yew:  burns slowly, with fierce heat, and the scent is pleasant.