Not only is it possible, but it's easy! You won't need more than a few pages to adequately explain how to generate simple light. I'll explain how, later, but first I'll answer your other questions.
My choice of location would be the late 1400s, to Leonardo da Vinci. He was a brilliant scientist and inventor, and would most likely understand the book and be able to carry out the instructions. More importantly, his exact location in both time and space is well known; you could send the book to his bedroom, if you wanted. And perhaps most importantly of all, not only are the materials required available, but he was at the very start of the scientific revolution. If his plans for a "light machine" were spread over the known world in the early 1500s, life would be very different indeed!
The very first wall you're going to hit is communication. Depending on where you send the book, you may have to write in a language that is radically different from today. English in the middle ages, for instance, is almost unreadable today, and vice versa. The smart choice would be to use Latin; most scientists read it fluently, and thus could pass the book around all over Europe. Remember also that a picture is worth a thousand words - use a diagram over a "word picture."
What the heck is this?
If you're sending the book back in time, you don't have the option to actually explain how this book works. Without that, you'll need to write a foreword, a page or two describing what this book is, what it intends to communicate, and how to read it. Explain things like page numbers, how to match the words "figure A" to the drawing, and so on.
Importantly, the cover should be waterproof and very garish; if it ends up under a bed somewhere, we want it to be visible, and if it ends up outside, we don't want it getting soaked and ruined.
Copper, gold, silver, and iron weren't all that hard to come by in the middle ages, or even earlier. Magnetic materials are a little harder to come by, but not unheard of. To make electricity, you need something to carry it. Copper is a good choice because it's flexible and has a low internal resistance, though really any metal will do. Don't bother explaining electricity, unless you have some room in the footnotes; if the person you send this book to can use your plans, they'll figure it out in short order. Just explain how to make wire, how to insulate it with varnish, and how to wrap it, join it, or otherwise work with it.
Motors and generators
A motor in reverse is a generator; wrap some wire in a big loop, stick a magnet on a spindle in the middle, and crank - instant electricity! Make sure to include instructions for finding the north and south poles of a magnet, and the proper direction to align them. A multi-step process with better and better motors may seem like a good way to go, but a better approach is to show the plans for the best motor possible (multiple windings per core, multiple cores on a spindle, etc.).
Finally, tie it all together. Connect the wires from all the windings into a big bundle, with one big wire coming out of the "start" and the "end" wires. At this point, you have a working hand-crank generator. Or, scaled up, a huge water-driven or mule-pulled generator. Either way, you can make some big sparks.
If you'd like, a short note on how to feed this energy back into a motor (with heavier wire) would be a fantastic way to note how practical all this is. Imagine the endless possibilities of water power in the early 1500s!
If there's space afterwards, you can explain the physics, but for now, we just want to build a light. Speaking of...
Light bulb moment
Don't try to create a light bulb - or at least, not one of today's standards. Instead, you'll want to make either a carbon-filament light, or just a simple spark light. The second is easy - inside a big blow-glass ball, have the two ends of the wires really close to each other. When the generator is turned, sparks will jump the gap; the more power from the generator, the brighter the light. This isn't an efficient light bulb; it isn't particularly bright, either. Still, it's a light, right?
A carbon filament bulb will be much, much brighter, but won't last as long. Two carbon tubes next to each other, with current applied, with glow as bright as the sun for a little while. Not long, but enough to really leave an impression. Edison used a carbonized bamboo filament with great success, lasting over 1200 hours in good conditions.
The first vacuum pump wasn't discovered until 1650, 148 years after Leonardo's death. However, with the right help, it wouldn't be too hard for the inventor to come up with his own version. However, technology would not be in place for some time to create enough vacuum to produce modern filament light bulbs. So, devote a few pages to explaining how a vacuum pump works, and how to create an efficient version. With the right carbon filament and enough of a vacuum, a bulb should last over a thousand hours - far more than a candle or a simple oil lamp.
Exotic materials and Other Information
Today, we use tungsten, because it has a high heat tolerance; however, not only would it be almost impossible to find, it would also be hundreds of years before machines were advanced enough to make a filament. LEDs and fluorescent tubes would also require materials that wouldn't be available or produce-able for centuries. Still, writing it down would be useful; even if the first inventor never made it, his successors would surely find a way.
In fact, all these explanations should only be a handful of pages; it's really not that hard to make wire, make the wire into a generator, and make a bulb that the generator powers. So, devote the rest of the pages to the science of electricity: transformers and motors, generators driven by water, wind, steam, or horse-power, AC, DC, voltage, current, resistance, even capacitors, inductors, and various micro-circuits. Include mine locations to dig up any metals or minerals needed to make modern circuitry, and modern maps to guide them. Circuits for telegraphs, radios, even television are simple enough to be included. The sky's the limit! Explain as much about modern machinery as possible; the more information available, the faster scientists and inventors will be able to create it.