1. Not being old enough to invent, I content myself with narrating, and I beg the reader to assure himself of the truth of a story in which all the characters, with the exception of the heroine, are still alive.

结构剖析：这是一个有并列连词and连接的2个并列分句。

（1）第一分句是：Not being old enough to invent, I content myself with narrating。在这个分句中，not being old enough to invent是否定结构的现在分词短语作原因状语，可以改之为原因状语从句：because I am not being enough to invent。

（2）第二个分句是：beg the reader to assure himself of the truth of a story in which all the characters, with the exception of the heroine, are still alive。在这个分句中，含有一个限定性定语从句：in which all the characters, with the exception of the heroine, are still alive。它修饰前面的名词story。Story在这里做为先行词，指代物，在定语从句做介词in的宾语。这样，可以把in提到定语从句的句首再接关系关系代词which，即：in which
此外，这个定语从句中的with the exception of the heroine是介词短语做定语修饰characters。

2. And thanks to a particular circumstance, I alone can write these things, for I alone am able to give the final details, without which it would have been impossible to make the story at once interesting and complete.

结构剖析：这个句子是由并列连词for而连接的2个并列分句。

（1）第一个分句是：and thanks to a particular circumstance, I alone can write these things。在这个分句中and是副词，起到承上启下的作用，thanks to是作为符合介词，表示原因。

（2）第二个分句是：for I alone am able to give the final details, without which it would have been impossible to make the story at once interesting and complete.

在这个分句中for属于并列连词，表示原因。 这个分句中含有一个非限定性定语从句：without which it would have been impossible to make the story at once interesting and complete。

这个非线性性定语从句的引导词是without which，其中的which是指代前面所说的情况——and thanks to a particular circumstance, I alone can write these things，for I alone am able to give the final details（由于特殊的情况，只有我一个人知道事情的来龙去脉，我一个才能写出这些事情。）因此，without which意思就是“没有这种情况的话”。

此外，这个定语从句使用“it”做形式主语，动词不定式“to make the story at once interesting and complete”做真实主语。