ば〜ほど details
write + if + the more you do X, the more Y — proportional escalation between two clauses
kakeba kaku hodo
the more you do X, the more Y — proportional escalation between two clauses
実は、読めば読むほど、この本は面白くなるんだ。
jitsu wa, yomeba yomu hodo, kono hon wa omoshiroku naru n da.
Honestly, the more you read this book, the more interesting it gets. casual
値段は高ければ高いほど、品質も良くなる傾向がある。
nedan wa takakereba takai hodo, hinshitsu mo yoku naru keikou ga aru.
The more expensive the price, the more the quality tends to improve too. neutral
Examples
the more X, the more Y — a correlative scale between two clauses, or a degree that intensifies together with itself
実は、読めば読むほど、この本は面白くなるんだ。
jitsu wa, yomeba yomu hodo, kono hon wa omoshiroku naru n da.
Honestly, the more you read this book, the more interesting it gets. casual
値段は高ければ高いほど、品質も良くなる傾向がある。
nedan wa takakereba takai hodo, hinshitsu mo yoku naru keikou ga aru.
The more expensive the price, the more the quality tends to improve too. neutral
資料は確認すれば確認するほど、新しい問題が見つかるものです。
shiryou wa kakunin sureba kakunin suru hodo, atarashii mondai ga mitsukaru mono desu.
As a rule, the more you check the documents, the more new problems turn up. formal
Formation
{V-ba}{V}ほどattaches to ば conditional stemi-adj stem + ければ + i-adj + ほど（高[たか]ければ高[たか]いほど）attaches to i-adjective
Notes
ほどいい "the more the better," short for 多ければ多いほどいい.
な-adjectives and nouns use であればあるほど in writing (上手で
あればあるほど) — never ×学生なほど.
Related patterns
Similar
につれて narrates a GRADUAL external progression across two clauses, often with different subjects and no explicit "if" framing (物価[ぶっか]が上[あ]がるにつれて、生活[せいかつ]が苦[くる]しくなる); 〜ば〜ほど is an explicit conditional correlative doubling the SAME verb or adjective, and unlike につれて it attaches directly to adjectives too (高[たか]ければ高[たか]いほど).
Lookalikes
Same ほど, unrelated grammar — the ほど in 〜ば〜ほど builds a correlative "the more, the more" scale together with a ば-clause, while ほど〜ない caps a comparison under a NEGATED predicate in a totally different frame (死[し]ぬほど疲[つか]れた is a different, positive-extent ほど entirely) — seeing bare ほど doesn't by itself say which construction you're in.