Q. I've been getting my friends to post reviews of my book on Amazon, and --
A. Yes. We can tell.
Q. A horrendous and tragic event just happened (huge explosion, bubonic plague, terrorist attack, catastrophic storm), with considerable loss of life and general devastation. This event shares a number of details with the plot of my thriller novel. Wouldn't this be a good moment to do tie-in promotion on my book? You can't say it isn't topical.
A. No. That's a terrible idea. You'll come across as saying "Remember that incredibly upsetting recent event? Let's forget about the victims and their families, and instead make it all about MEEEEE!" Many people will be genuinely repulsed by your pitch. Some will also find it memorable. You don't want that.
Q. I've been looking for forums and comment threads on subjects that relate to my book, and posting comments (with links) that discreetly allude to it. The pages I link to are getting more hits, but I'm not selling more copies. How can I fix this?
A. The only way you can "fix" the situation is by not spamming other people's conversations in the first place. What you're doing is rude, and will not sell books. The people whose forum you're abusing will recognize your intrusion for what it is, resent you, and extend their resentment to your book on general principles. And if it's a forum that preserves its old threads, your spam will be recorded there forever.
Q. I've been offered a chance to buy a professional direct-mail list of 50,000 e-mail addresses, plus software that will automatically send copies of my on-publication press release to all addresses on the list. What percentage of the people who receive my press release are likely to buy a copy of my book?
A. Zero. What you're being offered is a basic spam setup. The rate of return on spam is infinitesimally small. Also, you'll be a spammer, so if you're determined to do this, start stitching a scarlet "S" now so you'll have it ready to pin on your chest.
Even if you used a legitimate mailing list, your rate of return would be tiny. As a rule of thumb, any piece of promo that isn't accompanied by a copy of the book is a waste of time. At most you might drum up a few nonfiction sales, because in nonfiction it's the subject that sells; but it would still be an ineffectual approach.