"Highly recommended for capable students as a source of interesting review and challenging word problems"If you've ever used the books, you know what a loss this will be to future users. While the books may be relics compared to the current Singapore Syllabus, one can't help wonder if the changes in the "Teach Less, Learn More" syllabus in Singapore haven't contributed to the country's ever so slight drop on the most recent TIMSS.
SingaporeMath.com may have most books in the series available through summer, although it sounds like Primary 3 is in short supply.
For your problem-solving enjoyment, here's a sample from the end of the Primary 6 book - Challenging level:
Cindy had four times as many postcards as Annie. After Cindy gave 20% of her postcards to Jane and Annie gave 10% of her postcards to Jane, the number of Jane's postcards increased by 75%. If Jane had 252 postcards in the end, how many postcards did Cindy have at first?Have fun!