The scroll, wand, and spellbook of light should all weigh less than other objects of those classes. This makes them trivially identifiable, but it isn’t considered game breaking to be able to tell these 3 objects.

The spell of light has an advanced form that makes you a light source for some temporary length of time, flavored as summoning an incorporeal globe of light that follows you around.

Angering peaceful monsters by casting an innocuous spell like light is very annoying, so split the spell up into a “light area” spell, which does not damage anything unless it’s a highly light-sensitive monster like a gremlin, and a “light blast” or “flash” attack spell, which may or may not light the area permanently and is designed to blind monsters.

Some ways to scale some spell effects with skill. Generally, this consists of nerfing unskilled and basic casting rather than adding even more powerful high-skill effects.

• Beam spells such as knock and wizard lock scale the range of their beam with skill, with only a few squares at Unskilled, up to 4 squares at Basic, up to 6 at Skilled.
• Identify always identifies exactly 1 item when Unskilled.
• Light scales its radius with skill.
• Charm monster only pacifies 1 monster at Unskilled, and can only tame 1 monster at Basic, 3 at Skilled, no cap at Expert.

Move the spell of light to the clerical school.

The spell of light has an advanced form, which is a ray. It blinds monsters it is fired at like a camera flash does. (The camera flash is also transformed into a ray, which can be reflected.) In Wands Balance Patch-implementing variants, the wand of light should also have this effect for skilled users.

Izchak sells scrolls and wands of light, maybe spellbooks too, at low frequencies.