May 31--Born a son of a Japanese trading- company executive, and exclusively educated in Britain, Tetsuya Ishikawa got his first taste of life in the financial industry in the summer of 1998. That was during his pre-university "gap year," when he worked on the foreign-exchange trading floor at the Tokyo branch of Chase Manhattan Bank, which is now a part of JPMorgan Chase.

Attracted by the industry's prestige, and inspired by the meritocratic culture he experienced during his time with Chase Manhattan, he jumped into banking after graduating from Oxford University in 2001, joining the London office of the Dutch bank ABN AMRO. Though he didn't know it then, in the following six years, as he worked as a "credit banker," he would be taken to the very heart of the financial activities that helped create a credit bubble. But when the bubble burst, shock waves quickly spread worldwide. Several gigantic financial institutions were wiped out or driven into nationalization; Iceland's economy virtually collapsed; and the world is now experiencing possibly the worst ever financial and economic downturn.

Though still a mere 30 years old, Ishikawa -- who has also worked at Goldman Sachs and Morgan Stanley -- came out last month with a thinly fictionalized account of what has happened to his life, the credit markets and the financial system he worked in.

Sensationally titled "How I Caused the Credit Crunch" (Icon Books), the book tells how a young university graduate with no grasp of terms such as "securitization" or "credit derivatives" turns into an overnight expert on investment products founded on such financial concepts.

In fact, as the book explains in straightforward language, securitization is a process in which assets such as mortgages and corporate loans are pooled together and then repackaged as securities according to their risk. These are then sold to investors who weigh the risks and likely returns before buying in -- with rates and returns generally higher where the risk of debtors defaulting was higher.

The catch was that even financial products awarded a AAA rating by agencies specializing in such assessments were not risk-free. Nor could they be guaranteed to keep their rating indefinitely. We know now that as the bubble burst and U.S. housing-loan defaults started to skyrocket in 2007, ratings for many assets previously thought to be the safest went through downgrade after downgrade. The implosion, in fact, was painfully reminiscent of the bad-loans quagmire Japan experienced throughout the 1990s after the burst of its asset-inflated economic bubble.

Ishikawa, who was laid off by Morgan Stanley in May 2008 and now lives in London with his Korean wife and two young children, says it was not feelings of resentment or bitterness toward his former employers or the industry that inspired him to write the book.

"I actually don't feel any sort of resentment," Ishikawa said in a recent telephone interview, noting that it was the "paucity of the press coverage" about what exactly happened during the credit bubble and crunch that motivated him to tell it all.

His first attempt at writing has paid off, and the book gives a rare inside glimpse into the world of those credit bankers.