I think it's a matter of taste. I believe glass tops are fine. 1/4" should be plenty, 1/2" will look funny, IMO. You do want to have an air space underneath. Otherwise, liquids will wick in via capillary action and you can destroy your table before you realize it. Avoid the clear plastic "bumpons" as spacers. These can eat through a finish via a phenomenon known as "plasticizer migration." I always recommend stick-on felt pads to people. About 30 years ago, I had a cabinet shop make a slip-on cover for my wood table. We used it for every-day use when we had 3 young children. It is similar to an island countertop, but slips right over the table and slips off for formal use or to add leaves. One of my daughters is having one made for her everyday table as we speak. Ours and hers will be covered with HPDL ("Formica") in the color and style of choice. Just for reference, her cabinet shop is quoting her just under $400 for her topper.

Recommend you purchase clear tubing size of chair part hitting the table edge. Cut the tubing to the length that will meet contact with the table. Then cut a straight line down the piece of clear tubing and slip on the chair area. Do this for each chair. Now your table will stay protected and the clear tubing will be hardly noticeable on the chairs. Good luck.

My cookbooks are far from rare, unless you count my red and white checked Better Homes & Gardens that is circa 1953 and sadly bespattered, but I would still like to have kitchen shelves to put them on. They are presently in a small bookcase in the eating area and in the kitchen cabinet over the refrigerator where I would have to climb on a stool to reach them. As you can guess, those are the ones I never use (includes Julia Child's Art of French Cooking, which was a gift that I did read but never attempted a recipe). I love those beautiful old libraries, too, and just saw the one at the Royal Monastery of St. Lawrence in El Escorial, Spain, this fall. It is listed as one of the most beautiful in the world and left me speechless.

Keda makes dyes with water/alcohol/solvent bases, so the type you choose will also have some input on the finish. Water based finishes generally do not add color tints. Shellac comes in many colors and oil based finishes add an amber tone. The following paragraph is from their finishing tips on their web site: " Sealing We recommend using a UV protecting sealer over the dried wood dye stain in order to protect the color. If you choose not to use a UV sealer, the color can still last for a long time as long as you keep the wood finishes out of direct sunlight. When applying the first seal coat, we recommend applying a very light, thin coat with minimal rubbing, and then let it dry. This will seal the wood dyes and help prevent any possible reactions. Apply subsequent coats of wood sealer according to manufacturer's recommendations. After sealer cures, follow up with wet sanding and polishing if desired."