The Gold Deadline is the second in Herbert Resnicow’s Norma and Alexander Gold series, which was originally traditionally published back in the 1980s. It is free right now at Kindle US and UK.
In addition, the first title, The Gold Solution, is long term at $0.99/£0.99 so if you’d like to read in order, it won’t be too expensive to try both together.
The Gold Curse is the fourth in this series. It is free right now at Kindle US and UK. It has been free for a little while, so grab it fast if you want it…
Kindle US: https://www.amazon.com/dp/B01LWSFAIY
Kindle UK: https://www.amazon.co.uk/dp/B01LWSFAIY
The Gold Deadline is free again right now at Kindle US and UK, and the first title in the series, The Gold Solution, is still long-term at $0.99/£0.99. So as mentioned in the OP, if you’d like to read in order, it won’t be too expensive to try both together.
And the links in the OP are still good.