Statement: Never before such a lucid book was available on the topic. Assumptions: Some other books were available on this topic. You can write lucid books on very few topics.

Given data

• Statement: Never before such a lucid book was available on the topic.
• Assumption I: Some other books were available on this topic.
• Assumption II: You can write lucid books on very few topics.

Concept/Approach

The superlative comparison ('such a lucid') presumes earlier availability for comparison; it does not generalize about other topics.

Step-by-step reasoning
Saying 'never before such a lucid book' implies there were earlier books (less lucid) on the topic ⇒ I is assumed.Nothing is implied about the possibility of writing lucid books on other topics ⇒ II is not assumed.

Verification/Alternative

If no prior books existed, the phrasing would more naturally be 'This is the first book on the topic,' not a comparative claim about lucidity.

Common pitfalls

• Reading an unwarranted general rule about lucidity across topics.

Final Answer
Only assumption I is implicit.