THE TESSERACT IS a thriller. Novelist Alex Garland sets the opening scene in a seedy Manila hotel room, where a young, nervous, drug-dazed ship's officer prepares to meet a legendarily ruthless mestizo gangster. The purpose of the meeting is to arrange protection for his English freighter against pirates in the South China Sea. Idly killing cockroaches while he waits, the officer reflects, "Everything weird was the bottom line." For instance, the eerie emptiness of the hotel, the spattered blood on the sheets, the patterned cigarette burns on the inoperative telephone, the metal disk screwed over the peephole--from the outside. Garland can really write, and