So the question is
are there any techniques for speeding up these kinds of queries?
Well, not really. A column-based storage engine would probably be faster with those SELECT COUNT(*) queries but it would be less performant for pretty much any other query.
Your best bet is to maintain a summary table via triggers. It doesn’t have much overhead and the SELECT part will be instantaneous no matter how big the table. Here’s some boilerplate code:
DELIMITER //
CREATE TRIGGER ai_books AFTER INSERT ON books
FOR EACH ROW UPDATE books_cnt SET total = total + 1 WHERE status = NEW.status
//
CREATE TRIGGER ad_books AFTER DELETE ON books
FOR EACH ROW UPDATE books_cnt SET total = total - 1 WHERE status = OLD.status;
//
CREATE TRIGGER au_books AFTER UPDATE ON books
FOR EACH ROW
BEGIN
IF (OLD.status <> NEW.status)
THEN
UPDATE books_cnt SET total = total + IF(status = NEW.status, 1, -1) WHERE status IN (OLD.status, NEW.status);
END IF;
END
//