My backyard is situated very close to what was an old brick quarry (clay pit). Therefore, the soil is very dense. I would like to buy a rototiller to improve the soil, but some gardening books say that this is not a good idea. Is a rototiller a wise option?
A lot depends on the size of the garden you have in mind and how fast you want to improve the soil. The bigger the garden and the sooner you want improvement, the more a rototiller can help. On the other hand, a rototiller costs a lot of money and won’t help much after the first year or two. Why not hire someone to till your garden the first year?
I would bring in a lot of organic matter, spread it 4 inches deep over the entire garden, and have it tilled into the top 8 inches of soil. Ask a landscape contractor for a bid, ask at your local nursery or garden center for people who till for an hourly rate.
By the way, if your soil consists mainly of clay for the first two feet, I recommend you garden on raised beds. When you finish tilling, decide where you want paths and shovel the tilled soil from the paths onto the beds (you can fill the paths with mulch, such as wood chips). You’ll need raised beds to give your plants enough root room and drainage.
Finally, I used to till and then stopped. I’m fairly convinced that most of us can garden just fine with a spade and a garden fork. Tillers chew up the soil and break up its structure. Over a few years, you get heavier soil, not lighter soil, unless you constantly add lots of organic matter. On the other hand, a soil in good tilth will yield well year after year with less than an inch of new organic matter added every spring, and I know firsthand that if you avoid walking in your garden beds, and avoid tilling them, the soil improves steadily (thanks mainly to soil critters, especially earthworms).